Solved it! It was a combination of many solutions presented above, but I just had to put them in the right order:

From Windows Explorer, delete the old Google Drive folder from your computer. If you haven’t already done so, log in to your Georgetown Google Apps account. From your Web browser, go to the Google Drive File Stream home page. On the Google Drive Help page, click on Download for Windows. In the following pop-up window,. With Google Drive File Stream, the contents of your Google Drive appears on your Mac like a regular drive. Unlike Google Backup & Sync (and the old Google Drive app), the files are not all copied to your computer. This saves a lot of space on your drive and almost eliminates sync errors.File Stream is only available for Google Apps G-Suite users. Drive File Stream Access all of your Google Drive content directly from your Mac or PC, without using up disk space. Download Backup and Sync for Mac Download Backup and Sync for Windows.

I deleted the Google Drive File Stream app, emptied the trash

I reinstalled the app (still gave an error when trying to log in)

I went to the Finder folder Library --> Application Support --> Google.

I renamed the folder DriveFS to DriveFS.old

Download Google File Stream For Mac

I was now able to log into the app, but it still gave an error accessing the files:

I then went to GO --> Utilities --> Terminal in order to overwrite the Gatekeeper

I entered: sudo spctl --master-disable

Then I entered my password (it’s not visible that you enter something, but the key strokes are noted)

After this I went to system preferences --> Security & Privacy

Under ‘Allow apps downloaded from’ the option ‘Anywhere’ was now visible and automatically enabled

Apps Drive

Also, it now showed the text ‘System software from developer “Google, Inc.” was blocked from loading’. --> click 'Allow'

Download Photos To Google Drive

Then when reopening the app, it would start downloading all my files.