M365
Microsoft 365 errors and fixes
Sign-in, activation, Outlook, Teams, OneDrive and SharePoint errors that block work on managed and personal accounts.
Flagship articles
Highest-priority pieces in this category — the ones we're most confident solve the problem.
Microsoft 365 Error CAA50021: What It Means and How to Fix It (2026 Updated Guide)
CAA50021 is a Microsoft 365 work/school account sign-in error. Here's what it actually means, the one fix that resolves most cases, and when to stop and call IT.
caa50021
Office Activation Error 0x80070005: How to Actually Fix It (2026 Updated Guide)
Office activation fails with 0x80070005 because the identity layer is broken — not because Office can't reach the internet. Here's the fix path no one writes about.
office activation error 0x80070005
OneDrive Error 0x8004de40: What It Means and How to Fix It (2026 Updated Guide)
OneDrive error 0x8004de40 means the client can't connect to the cloud. Here's exactly what the code means, the real causes, and the fix order that works.
onedrive error 0x8004de40
Premium fixes
High-value troubleshooting for microsoft 365 — written and verified by our editors.
Office Keeps Asking Me to Sign In Every Time: Why Tokens Don't Persist (and How to Make Them)
If Microsoft 365 asks you to sign in every time you open Word or Excel, the token isn't persisting to disk. Four root causes and the fix order that resolves them.
office keeps asking me to sign in
Outlook Keeps Asking for Password: The Modern Auth Fix Order (Not the 2018 One)
Most 'Outlook keeps asking for password' guides are 2018-vintage Basic Auth fixes that no longer apply. Here's the modern fix order for Microsoft 365 in 2026.
outlook keeps asking for password
Microsoft 365 Apps Won't Activate After Update: How to Fix It (2026 Updated Guide)
Office activation breaks after Windows updates because the update touched the credential subsystem, not because Office is corrupted. Here's the actual fix sequence.
microsoft 365 won't activate after update
Microsoft 365 MFA Prompt Loop: Three Patterns, Three Fixes
Microsoft 365 MFA prompt loops aren't one problem — they're three. Here's how to identify which pattern you're seeing, and the fix for each. End-user and admin paths.
microsoft 365 mfa prompt loop
Microsoft 365 'Something Went Wrong' Sign-In Error: How to Read the Bracket Code and Fix It
The 'Something went wrong' Office sign-in error has a code in brackets. Here's how to read [1001], [4vt9f], [657rx], and the rest — and the fix order that actually works.
microsoft 365 something went wrong sign in
OneDrive Error 0x8004de90: What It Means and How to Fix It (2026 Updated Guide)
OneDrive error 0x8004de90 means your account isn't fully set up — usually a license or provisioning issue, not a network problem. Here's the fix.
onedrive error 0x8004de90
By topic
Browse microsoft 365 fixes by subcategory.
Sign-in & work-school account
3 articlesOffice activation
4 articles- Office Keeps Asking Me to Sign In Every Time: Why Tokens Don't Persist (and How to Make Them)
- Microsoft 365 Apps Won't Activate After Update: How to Fix It (2026 Updated Guide)
- Office Activation Error 0x80070005: How to Actually Fix It (2026 Updated Guide)
- Microsoft 365 License Assigned But Apps Won't Activate: The Real Fix (2026 Updated Guide)
Outlook
5 articles- Outlook Keeps Asking for Password: The Modern Auth Fix Order (Not the 2018 One)
- Outlook Disconnected from Server: Why It Happens and How to Get Back Online (2026 Updated Guide)
- Outlook Error 0x800CCC0E: What It Means and How to Fix It (2026 Updated Guide)
- Outlook Search Not Working: Why It Breaks and How to Fix It (2026 Guide)
- Shared Mailbox Not Showing in Outlook: Why It Happens and How to Fix It (2026 Updated Guide)
OneDrive & SharePoint
4 articles- OneDrive Error 0x8004de40: What It Means and How to Fix It (2026 Updated Guide)
- OneDrive Error 0x8004de90: What It Means and How to Fix It (2026 Updated Guide)
- OneDrive Sync Pending Forever: How to Identify Which Sync State Is Actually Stuck
- SharePoint Access Denied When You Have Permission: The Four Real Causes (2026 Updated Guide)