This is likely due to a PST being accessed from a network drive location which now a no-no. All PST/OST's should be opened locally on the PC going forward.
Go to Control Panel>User Accounts>Mail(Microsoft Outlook)
Then go to Data Files
From here, you should see the location of the pst that's on a network drive (more than likely in U:\ location). Go ahead and select the problematic pst and remove it
You Then want to copy the pst from the network drive to the C:/ drive. (I generally like to put it in "C:\Users\(username)\Documents\outlook files"
You may run into an issue where the outlook file that you copied may say it's corrupted, in that case you can try repairing it via scan pst "C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE"
If the pst still says that it's corrupted then you'll need to loop in infrastructure to recover the pst to an earlier date before it was corrupted, copy it locally and then try again.
Now, you'll want to open the file from the new path which should open back up in outlook After that ideally outlook should then play nice.
***Possible fix not needed to do anymore***
This seems to be due to a recent update:
**This will Modify the windows registry. Be very cautious as to modify only the specificed locations.This can potentially break windows if not done properly**
In order to resolve, you want to recreate the Outlook registry opening regedit and HAVING THE USER PUT IN THEIR PASSWORD (otherwise this won't work)
After doing so go to:
Computer\HKEY_CURRENT_USER\Software\Microsoft\Office
Then change the following registry entries to Outlook.old:
Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook
Computer\HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook
This will force Outlook to recreate the registry entries and should resolve the issue.