Since migrating to Cloud Identity (without G-Suite), we have found the authentication blocks us from a number of shared resources in the Google domain.

e.g. Google Sites or Calendars shared with us cannot be accessed (although they could with Google consumer accounts).

Note that this is caused by our Cloud Identity accounts not having a G-Suite subscription. We are not trying to create or edit Sites - this relates to a site published by a third party (in this case Google!) and shared with us. The site is not accessible, even for read-only viewing.

We receive the message 'We are sorry, you do not have access to this service'.

I believe this is the authentication logic checking if you have a G-Suite license prior to checking whether the site/calendar is shared with you.

My suggestion is therefore to modify the authentication model to check whether a resource has been shared with the logged in account prior to checking what licensing permissions that account has.