Log in requested at each application start up.

Perform the following steps to stop Microsoft 365 apps from asking to sign in every time:

1. Close all Office apps.
2. Clear cached identity and auth data so Office can rebuild a clean sign-in state:
   • Open File Explorer and go to:
     • C:\Users\<YourUserName>\AppData\Local\Microsoft\
   • Delete the folders:
     • IdentityCache
     • OneAuth
3. If the device was previously connected to a work or school account that is no longer used, remove stale connections and cached credentials (if applicable):
   • Open Control Panel → Credential Manager → Windows Credentials and remove any entries related to old Microsoft 365/Office or organization accounts.
   • Open Settings → Accounts → Access work or school and disconnect any old organization accounts that should no longer be attached to the device.
4. Restart the computer.
5. Open one Office app (for example, Word) and sign in once with the correct Microsoft 365 account. Confirm the “Stay signed in”/“Remember” options if prompted.
6. Close and reopen the Office apps and verify that the sign-in prompt no longer appears each time.

If the problem persists on a Mac specifically and you see repeated prompts or “Authentication Session Expired,” also reset Office’s keychain permissions:

1. Quit all Microsoft 365 for Mac apps.
2. Open Keychain Access (search “keychain” with Spotlight).
3. Select the login keychain, then from the File menu choose Lock Keychain "login".
4. Open an Office app (such as Word).
5. When prompted for keychain access, enter the Mac admin password and select OK (and allow access).
6. Sign in to the Office account if prompted, then close and reopen the app to confirm prompts stop.

If none of the above resolves the issue and the device is domain-joined with Active Directory sign-in, check for a SignedOutADUser registry key under HKEY_CURRENT_USER\Software\Microsoft\Office<x.0>\Common\Identity and remove it so automatic sign-in can resume. Back up the registry before editing.

References:

• How to fix the issue with MS Office asking you to log in every time you open an Office app - Microsoft Q&A
• Office for Mac repeatedly requesting keychain access
• Microsoft 365 users aren't automatically signed into an Office app through Active Directory accounts after they sign out