Hi Felix,
This is due to recent changes on the Microsoft side. Adobe campaign uses the v8.2 in the API calls to MS Dynamics for API calls and it look like this has been identified as an issue with MS CRM per:
https://community.dynamics.com/365/f/dynamics-365-general-forum/388158/retrieveallentities-does-not-...
We have had success working around this issue by tweaking the out of the box connector code in Adobe campaign to force it to use version 9.1 of MS CRM. The crm:extAccount schema needs to be extended and the value of 'Dynamics CRM 365' needs to be updated to 9.1 in the msCrmApiVersion enumeration.
Once that is done the sync should work to pull the tables. This looks like it is also supposed to be updated as part of the product in later releases but is still in testing.
Regards,
Craig