Integration with Google Groups API, and OAuth2

Has anybody successfully created a connection to Google Groups using OAuth2?

Had a long session with Zoho Support today, and neither I nor they could work it out. Essentially:

- new custom connection to Google Groups, like all connections, requires completion of settings shown in attachments 'Zoho Connection creation' x2

- In the corresponding Google API section ("Google Credentials' attachment), I've created credentials (details of which are inserted above)

- When the connection is created, Google returns an error '400' redirect_uri_mismatch. Screenshot attached, and full text is:

client_id=599692313346-jem2bvqbnh92a45gq0goda<snip>apps.googleusercontent.com

redirect_uri=https://deluge.zoho.com/delugeauth/callback

response_type=code

scope=https://www.googleapis.com/auth/admin.directory.group.member,https://www.googleapis.com/auth/admin.directory.group.readonly,https://www.googleapis.com/auth/admin.directory.group.member.readonly,https://www.googleapis.com/auth/admin.directory.group

state=675185014__675185014__666710279__203033

There appears to be no area in the Google API panel to insert the redirect_uri, but it does appear to be passed correctly by Zoho, as it is returned in the Google error message. This uri (https://deluge.zoho.com/delugeauth/callback) is correct, according to Zoho Support.

So I am at a loss....

Failing that, have you managed to create an OAuth connection without using a Zoho custom connection - i.e. by using a service account, through invokeUrl so similar?

All help and thoughts most appreciated!

Thanks, Cam.