Hi IBN,
Do you have the same problem with other Office applications?
To better understand your problem, could you provide specific screenshots? If the sign-in window shows a blank authentication screen, you can refer to the Can't sign in to Microsoft 365 Windows desktop applications - Microsoft 365 | Microsoft Learn
Besides, try clearing Caches/Cookies and see if the issue appears.
If the issue continues, you might try the steps in this link: Office 365 keeps trying to sign in while I'm in Word - Microsoft Community
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