OK this is now resolved. The hosts whitelisted the file but forgot to release it. Everything now works as it should. Thanks very much for all your help!
I have tried installing a backup of the older plugin, but this is not working and the same error is showing itself. I have deactivated all other plugins and tried just Connections to check for any incompatibility but with the same result.
Still struggling with this. I deleted everything again and reinstalled it and the file was missing. I added the file manually but it is still not working!