We did a Marketing Cloud Connect configuration on a new customer project and came across an issue we've never seen before and none of the usual integration fixes work:
- Sends from Marketing Cloud to SFDC records work fine (synchronization also works)
- Tracking is not populated back to Salesforce. It doesn't even create Email send records.
- When we try to initiate a send from within Salesforce we get the following error:
the integration log shows exactly the same:
*****2020-01-21 17:02:01.897|EXCEPTION|Insert failed. First exception on row 0; first error: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, record type missing for: Email Send: 
We checked record types: All 3 record types are available and the connector user has full access to those
- Support also hasn't been helpful beyond the standard steps we already tried.
Has anyone seen this before or even knows what can be done?
Thanks a lot! Stephan