RE: Dynamics 365 Connection Setup
Also did you do as it requests in the error message you posted ?
To upgrade your connection to use Common Data Service
Open the Microsoft Dynamics 365 Connection Setup page, choose the Enable toggle to turn off your existing connection to Dynamics 365 Sales.
Open the Common Data Service Connection Setup page, and choose the Enable toggle to turn on the connection.
After you enable the CDS connection, the Business Central CDS Base Integration Solution is deployed to Common Data Service.
Uninstall the Microsoft Dynamics 365 Business Central Integration solution from your Dynamics 365 Sales. For more information, see Uninstall or delete a solution topic.
On the Microsoft Dynamics 365 Connection Setup page, turn on the Enable toggle to connect to Dynamics 365 Sales.
After you enable the Sales connection, the Business Central Integration Solution is deployed to Sales. This enables integration with entities that are specific to Dynamics 365 Sales, such as sales orders, quotes, and invoices.
On the Sales Connection Setup page, choose Use Default Synchronization Setup to initialize the integration table mappings for Dynamics 365 Sales.