Windows
MFA sign-in loop after new phone setup
The account could not complete sign-in in Outlook/Microsoft Authenticator after a phone change. The technician reset MFA and confirmed the account could log in again.
Killed once by someone from XL.net, on 2026-09-19.
Affects
Versions
- Windows
Apps
- Outlook
- Microsoft Authenticator
What you see
- Repeated sign-in/MFA prompts
- Could not complete account login in Outlook
Why it happens
Likely The account's MFA registration was likely out of sync after the new phone was added.
When it shows up
A user gets stuck in an Outlook/Microsoft Authenticator login loop after moving to a new phone and the account will not complete MFA sign-in.
You are in this case if:
- Outlook sign-in fails after an MFA challenge
- Microsoft Authenticator keeps prompting during login
1 fix below
The steps that killed it
The steps are behind a quick check
There are two ways in and both take a few seconds. Signing in opens the steps on every bug page; so does reading the picture.
Or answer this
Drawing a picture for you.
Can't read it? Sign in instead.
Keeping it away
- Re-register MFA after changing phones before relying on Outlook sign-in.
Someone from XL.net killed this on a Windows computer on 2026-09-19. It is written up from that one repair, so it cites no outside page.