Microsoft 365 Sign-In Problems: A Step-by-Step Fix Guide

Microsoft 365 sign-in failures usually fall into a handful of predictable causes. Work through these before assuming your account is compromised or your subscription lapsed.

1. Confirm it’s not a Microsoft outage

Check status.office.com or search “Microsoft 365 status” before troubleshooting your own setup — widespread outages happen and there’s nothing to fix locally in that case.

2. “Your account or password is incorrect”

Double check you’re using the right account — many people have both a personal Microsoft account and a work/school account, and Outlook or Teams may be defaulting to the wrong one. Use “Forgot password” at login.microsoftonline.com rather than guessing repeatedly, since too many failed attempts can temporarily lock the account.

3. Stuck on multi-factor authentication (MFA)

This is the most common lockout cause. If your authenticator app was on a phone you no longer have, or the app got reinstalled and lost its saved accounts, you’ll be stuck at the MFA prompt with no way to approve it. For a personal Microsoft account, use the backup/recovery options at account.live.com/acsr. For a work or school (Microsoft 365 business/tenant) account, only an admin on that tenant can reset your MFA method from the Microsoft 365 admin center — a regular user cannot self-recover a lost authenticator on a managed business account.

4. “Your organization has blocked this app” or conditional access errors

Business Microsoft 365 tenants can restrict sign-in by location, device compliance, or app. If you see this message, the fix has to happen from the admin side (Entra ID / Azure AD conditional access policies) — no amount of retrying or clearing cache on your end will resolve it, since it’s an intentional restriction, not an error.

5. Sign-in loops or endless redirects

Clear cached credentials: on Windows, open Credential Manager and remove any saved Microsoft/Office entries, then sign in fresh. In a browser, clear cookies for login.microsoftonline.com and office.com, or simply try an incognito/private window — a corrupted cached token is a common cause of redirect loops that look like a password problem but aren’t.

6. The desktop apps sign in but show “something went wrong”

Fully sign out of all Office apps (File > Account > Sign Out in any Office app, which usually signs out everywhere), restart the computer, and sign back in. This clears a stuck local token cache that a simple app restart doesn’t touch.

When it needs an admin, not a user fix

If you’re on a business/work account and none of the above resolves it, the issue is very likely something only a Microsoft 365 admin for your organization can see and fix — an expired license, a conditional access policy, or an account state change. Trying more password resets at that point won’t help; it needs someone with admin center access.

The endless sign-in loop, and the two-minute fix

Outlook asking for your password repeatedly, accepting it, then asking again is usually a cached credential that has gone stale rather than a password problem at all:

• Windows: open Credential Manager from the Start menu, go to Windows Credentials, and delete every entry beginning with MicrosoftOffice or MSOpenTech. Restart Outlook and sign in once, cleanly.
• Mac: the equivalent entries live in Keychain Access under “Microsoft” — delete those and sign in again.

This resolves a large share of sign-in loops and takes two minutes.

Locked out by MFA

Multi-factor authentication is genuinely important, and it is also how people lock themselves out — a new phone, a wiped authenticator app, a number that changed. If you are an ordinary user, your organisation’s admin can reset your MFA methods in minutes.

If you are the admin and you have lost your own second factor, it is considerably harder: you will be working through Microsoft’s account recovery, and if that fails, a support ticket with identity verification. Plan for days rather than minutes. The lesson worth taking from it is to set up more than one method now — an authenticator app and a phone number and saved recovery codes — while you still can.

If sign-in problems hit several people at once, it is a tenant-level issue and not something to troubleshoot machine by machine. While you are reviewing account security, it is worth knowing how to spot a phishing email — compromised Microsoft 365 credentials usually start there.

We handle Microsoft 365 administration for small businesses in Manhattan, including the recovery situations that are hard to get out of alone.