Hi @Jakub Škácha ,
According to my research, this issue may be caused by duplicate tokens in the keychain or by moving Office to a different location than the default /Applications folder.
To resolve this issue, you can try the following steps:
- Update your Outlook for Mac to the latest version, some issues will be fixed in updates. Choose Help > Check for Updates
- Delete any cached passwords and modern authentication tokens from the keychain.
- Lock and unlock your login keychain.
- Grant access to the keychain when prompted and sign in to your account associated with Office.
Here is an additional document for your reference: Office for Mac repeatedly requesting keychain access
I hope this helps you fix the problem.
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