User account doesn't exist in this directory

in plain english

The username doesn't resolve to any account in the tenant the app is signing into. Almost always a wrong-tenant problem (B2B guest expected but missing, personal account hitting work tenant, deleted account, or typo).

most likely causes

• User typed the wrong UPN or signed in to the wrong tenant entirely
• External user expected as a B2B guest but no guest invitation was redeemed
• User account was deleted or soft-deleted (still in the recycle bin)
• User has a personal Microsoft Account but the app only accepts work/school accounts

fix path

1. Confirm the UPN — Entra portal → Identity → Users → search the UPN. If absent, check Deleted users.
2. For external collaborators: Entra → External Identities → All users → invite as guest, then have them redeem the invitation email
3. If the user has both a personal and work account: have them choose 'Work or school account' on the account picker
4. Check Sign-in logs to confirm the correct tenant ID was hit — wrong-tenant typos surface here as 50034 every time

seen in

Entra ID interactive sign-in · B2B guest first-time access · Microsoft 365 sign-in

related

• errno AADSTS50105