'Not Implemented' Error message on Send/Receive

Outlook Version 2018 (Build 14326.20348)

Win 10 version 21H1 (Build 19043.1165)

Outlook has stopped updating email  and shows the 'Not Implemented' Error when I click on 'send / receive all folders 'and I get the following error if I try and add a new profile 0x80040154.

I have run the repair wizard and deleted and reinstalled the Office apps without any success. The PC was rebuilt 4 weeks ago, because I had exactly the same issue with the previous build and I couldn't resolve it. Following the rebuild everything worked OK and Gmail email was getting synched without any issues - until now.

I have previously followed steps on other threads that try to deal with the 'Not Implemented'  issue, but nothing works. I've tried deleting all profiles, but when I restart Outlook and get prompted to create a new profile I get the 0x80040154 error. The profile name does get registered (Profile name appears in Control Panel:Mail:Profiles list ), despite the error and Outlook does open, but if I then try and add an email account, within Outlook  I get the 'Not Implemented' error. 

Can anyone advise as to what is going on to cause this repeated corruption and how do I fix it?