TL;DR: Office 365 sign-in: “Oops, something went wrong”

The fix only. No explanation, no diagnosis. Read the full article if any of this does not match what you are seeing.

1. Check the obvious first: the PC clock (within five minutes of real time), the date, and that the account is not locked or its password expired.
2. Sign out of Office, reboot, sign in again. This alone fixes a surprising share of these.
3. Clear the broken sign-in: Settings > Accounts > Access work or school, select the work account, Disconnect. Reboot.
4. Sign in again from inside an Office app (File > Account > Sign in), not from the Settings page.
5. If it still fails, check the device registration from an elevated PowerShell prompt:

dsregcmd /status

6. Look at AzureAdJoined / WorkplaceJoined and the SSO state. If the device is in a broken half-joined state, leave and rejoin:

dsregcmd /leave

dsregcmd /leave disconnects the device from Entra ID. On a managed PC, check with whoever runs your tenant first, and make sure you have a local administrator account you can still log in with.

7. Reboot, sign in as the affected user, then confirm the device shows as registered in Entra ID under Devices > All devices.
8. Last resort: create a new Windows profile and test there. If that works, the fault is in the old profile, not the tenant.

← Full article, with the diagnosis and the why