Microsoft 365 Not Working? The 9 Things to Check Before Calling IT
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A structured first look can separate a Microsoft service problem from an account, device, email, Teams, file-access or security issue.
“Outlook isn't working.” “I can't get into Teams.” “My files have disappeared.” These are reports every business recognises, but they are not yet diagnoses.
Microsoft 365 problems can come from Microsoft's service, one account, one device, an application, a permission change or a security incident. Structured checks establish the scope.
The sensible order
ESTABLISH THE SCOPE → GATHER EVIDENCE → CHECK OBVIOUS CAUSES → THEN CHANGE SOMETHING
1. Check whether Microsoft 365 itself has a problem
Ask whether the problem affects one person, one application or several people and services. If colleagues cannot use Outlook, Teams and SharePoint at the same time, a wider service or network issue becomes more plausible than a damaged local profile.
Microsoft's Service Health in the admin centre is the best place for an administrator or IT provider to check tenant-specific incidents. It shows affected services and whether a fix is in progress. If the admin centre cannot be reached, Microsoft's public status page is a fallback. Treat any outage report as evidence, not proof that every local symptom has the same cause.
Microsoft Learn: How to check Microsoft 365 service health →
Microsoft 365 public service status →
2. Check the user account
Can the affected user sign in at all? Is the failure a wrong-password message, an MFA problem, an account lockout, a disabled account or a message saying the user does not have access to a service? Those clues point in different directions.
- Try the normal Microsoft 365 sign-in page without repeatedly guessing the password.
- Note whether MFA arrives, fails, or was requested unexpectedly.
- Check whether the problem follows the user to another Microsoft 365 application, and ask the administrator or IT provider to confirm the account is active and licensed.
A licence or user-configuration change can look like an application failure. Do not alter identity or directory settings to test a theory. Capture the exact message and ask the responsible person to verify the account.
3. Try another device or browser
A second device or browser is a diagnostic comparison. If Outlook on the web works in a private window but the desktop application does not, the local application, session or browser may be the problem.
If the same error follows the user, it is more likely to involve the account, service, licence or network. If only one laptop fails, note its application version and recent changes. Do not delete profiles or reset synchronisation first.
4. Separate the email problem
“Email is broken” can describe several issues. Ask which is happening:
- Messages cannot be sent, or are stuck in the Outbox.
- New messages cannot be received, or are delayed.
- Only one sender or recipient is affected.
- The message is in Junk Email, quarantine or another folder, or a mailbox or attachment limit is involved.
Check Outlook on the web where appropriate and look for a non-delivery message rather than repeatedly resending. A large attachment, filtering rule or recipient-specific issue needs a different response from a mail outage. Do not change Exchange settings yourself.
Microsoft Support: I can't send or receive messages in Outlook →
Microsoft Support: Issues sending and receiving email →
5. Treat Teams as its own check
For Teams, identify whether the problem is joining a meeting, signing in, messaging, sharing, calling or using a microphone and camera. Try the browser version if the desktop application is the only thing failing; the browser may need permission to use the camera, microphone or speakers.
Check whether one person or several have the same problem. Guest and external access can affect one meeting without making Teams unavailable for the whole business.
Microsoft Support: Troubleshoot in Microsoft Teams →
6. Check SharePoint and OneDrive separately
A missing file is not automatically deleted, and a sync icon is not automatically a SharePoint outage. Check the browser copy, another colleague's access and whether one folder, one person or the whole site is affected.
- Permission or sharing issue: the file exists but one person cannot open it.
- Sync issue: the browser copy is current but the local folder is not.
- Moved, renamed or missing file: search and recent activity may help.
- Wider service issue: several users and sites show the same symptom.
Do not unlink accounts, delete local folders or carry out a destructive sync reset as a first response. Record whether the cloud and local copies differ, then involve IT if the distinction is unclear.
Microsoft Support: Fix OneDrive sync problems →
Microsoft Learn: Resolve OneDrive for work or school sync issues →
7. Check licences, users and permissions
Recent changes are valuable clues. Was a user created, moved between groups, had a licence or project owner changed, or was a permission tightened? A changed group can affect several applications.
Ask the person responsible for Microsoft 365 to compare the affected user with a working user. Verification is safer than repeatedly adding permissions or licences; extra access can become a security problem.
8. Know when troubleshooting becomes a security incident
STOP ordinary troubleshooting and contact your IT or security provider promptly if there are unexpected MFA prompts, unfamiliar sign-ins, suspicious forwarding rules, an unexpected password change, unusual messages sent from the account or security alerts you do not recognise.
A suspected compromise is not the time to keep testing passwords, delete evidence or make uncontrolled changes. Tell the provider what happened and what the user saw so they can protect the account.
9. Before you call IT
A good support request does not need a technical diagnosis. It needs useful evidence:
- 1Who is affected?
- 2What exactly happens, and in which Microsoft 365 application?
- 3When did it start, including the approximate time?
- 4What is the exact error message?
- 5Does it happen in another browser or on another device?
- 6Does it affect one person or several?
- 7Has anything recently changed?
- 8Can you attach a screenshot where it is safe to do so?
Do not randomly change Microsoft 365 settings
Changing several things at once can hide the original cause and create new problems. The goal is to identify the scope and collect evidence, not become a Microsoft 365 administrator in the middle of an outage.
Microsoft 365 Security Checklist: 7 Controls Every Business Should Review →
What Your IT Provider Should Monitor →
The IT Club view
Microsoft 365 is a collection of services, applications, accounts and permissions rather than one switch. “Microsoft 365 isn't working” can describe anything from a global incident to a possible compromise.
The useful habit
Find out how wide the problem is before you try to fix it.
A calm scope check does not replace IT support. It gives IT a better place to start and reduces risky changes.
Still not sure what is wrong?
If you've worked through the basics and still don't know what's wrong, send your question to Ask IT Club — including the symptoms and checks you've already completed.
Found this useful? Forward it to another business owner.
Sources and further reading
This is original IT Club commentary based on Microsoft's support guidance checked on 15 September 2026. Confirm current tenant-specific information before making a production change.
Microsoft Support: I can't send or receive messages in Outlook →
Microsoft Support: Troubleshoot in Microsoft Teams →
Microsoft Support: Fix OneDrive sync problems →
Microsoft Learn: Resolve OneDrive for work or school sync issues →
Plain-English Takeaway
Establish the scope, gather evidence, check obvious causes, then change something. Random configuration changes usually make troubleshooting harder.
Frequently asked questions
What should I check first when Microsoft 365 is not working?
First establish the scope. Check whether other people are affected, whether Microsoft has a known service issue, whether the user can sign in and whether the same problem occurs in another browser or device. This prevents a local problem being treated as a company-wide outage.
Should I reset Microsoft 365 settings to fix a problem?
Not as a first step. Changing several settings at once can hide the original cause and create new problems. Record the symptoms and checks already completed, then ask your IT provider to make a controlled change if one is needed.
How do I tell whether an Outlook problem is a Microsoft 365 outage?
Compare the symptom with what other users experience, check Microsoft 365 Service Health if an administrator or IT provider can access it, and try Outlook on the web or another device where appropriate. A single stuck message, full mailbox or recipient-specific failure points to a different investigation.
When should a Microsoft 365 problem be treated as a security incident?
Stop ordinary troubleshooting if there are unexpected MFA prompts, unfamiliar sign-ins, unexpected password changes, suspicious forwarding rules, unusual messages sent from the account or security alerts you do not recognise. Contact your IT or security provider promptly and avoid uncontrolled changes.
What information should I send to IT?
Send who is affected, what exactly happens, when it started, the full error message, whether another browser or device changes the result, whether others are affected, what recently changed, a safe screenshot and the approximate time. This gives IT a starting point instead of “Microsoft 365 isn't working.”
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