Error: Cannot open database...VFP02x
Cannot open database ... VFP02x. Fixed in SSMS v21.0.0.201.

This error is related to the database name being expanded to (Synchronized) or (Read-Only) for example. The AddIn was taking this name to establish a new connection to the database.
This error is fixed in SSMS v21.0.0.201. The AddIn is taking the internal database name property to create the connection.