Hi @mO_Ni_cA
Welcome to our forum!
Does the issue occur recently on Outlook Desktop Client? Do you have any specific operation before the issue occurred?
What is the version of your Outlook? It is recommended that you please check the Outlook client version (File>Office Account>Product Information) and try to upgrade to the latest version to see if the problem is resolved.
Have you ever turned on 2-step verification setup? As i know, turning on the two-step verification setting may cause Outlook to fail to connect to Gmail and keep asking for your password. If possible, you may want to go to https://myaccount.google.com/security and turn it off to see if there are any differences.
How did you add your Gmail account to Outlook? If the issue persists, it is suggested please try remove and re-add your account by the following steps:
File>Add account>Type your account and tick 'Let me set up my account manually', Connect>Choose IMAP>Wait a little, it may appear 'something went wrong', you need click Change Account Settings and the change Outgoing Mail port (587) and Encryption Method (STARTTLS)>Connect.
Meanwhile, you may go to Control Pane>User Accounts>Credential Manager>Windows Credential>From the drop, Remove all credentials of your Gamil account> Restart Outlook and enter your password.
If all above do not work, considering data file corruption, it is proposed that you create a new profile, re-add your account to the new profile and check if the same error still occurs.
Hope it helps.
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