[4vt9f] error occurs when connecting to Outlook

Question

I was going log in to Outlook, but the following error codes are continuously occurring.

Currently, in the case of Teams and Excel, it is logged in normally with the account.

Message: The credential is invalid.

Tag: 4vt9f

Answer 1

Dear @Tom D,

Based on the message "The credential is invalid" Tag: 4vt9f and the fact that your account can sign in successfully to Teams and Excel, the issue may be related to cached Outlook authentication credentials rather than the account itself.

In this case, please try these steps below and check if it works:

1.Removing all existing identification caches from these locations:

C:\Users\%username%\AppData\Local\Microsoft\OneAuth\blobs

C:\Users\%username%\AppData\Local\Microsoft\OneAuth\accounts

C:\Users\%username%\AppData\Local\Microsoft\IdentityCache

2.After clearing the cache, sign out of all Microsoft 365 accounts on the device.

3.Disconnect the work/school account from Windows:

• Open Settings > Accounts > Access work or school.
• Select the connected work/school account and choose Disconnect.

4.Reconnect the work/school account under Access work or school.

5.Open Outlook and sign in again.

If the issue persists, please let me know. Thank you for your valuable time and cooperation.  

I am looking forward to your response!

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