Now it seems to be over
I can still access Google Drive with the old app, as long as I keep my current Google Drive entry in the [|FSPlugin|cloudplugin] section of wcx_ftp.ini - but if I delete the Google Drive entry, I can no longer get a new.
So I installed version 2.80 of the plugin and after two attempts of enabling the Google API I got it to work.
Because "Google Drive API"
was not in the list of APIs I first thought they had changed the name, so I tried "Google Cloud APIs" but that did not work.
So maybe change item 5 in the API manual from:
5 Click on "Google Drive API"
to
5 Search for "Google Drive API"
Also there is a typo in item 33 in the API manual:
33 Pick the json file you downloaded above.
Altenratively, you can enter client id and client secret separated by a comma