Outlook data file cannot be configured

Hello,

 Office 365. Windows 11.

1.) I have a user that is receiving "Your Outlook datafile cannot be configured" pop-ups multiple times (30) during the course of an evening. During the day no messages come up. I have checked the pc itself, reinstalled 3x's, ran scanpst and SaRa. I wanted to create a new profile and I am unable to and receive "couldnt set up your account manually try setting the account up another way" I do it the other way, doesnt work.  Email works fine other than the data file message and wouldnt know there was an issue. 

2.) Also same pc, There are over 1,000  sameusername.nst files can I remove them? They data back from installation. 

3.) Im not sure if this is something that could be related. The inbox folder is larger than 4Gb. Some articles I have read said this is not a big deal but, I curious if this affects data file config? 

Im close to starting from scratch but I am not certain that would solve the problem. 

Thanks