Hello @Airwolf39_N_A and @logikoz ,
Welcome to The MongoDB Community Forums! 
Please check if SQL Schema is generated as the most common reason to this error is that the SQL Schema needs to be generated. Could you try running sqlGenerateSchema command on collection, and see if that clears up the error
To run the sqlGenerateSchema, you must do so from the admin db. Here are some instructions that might help.
If this does not resolve your issue, can you please share additional details such as:
- what steps did you follow before getting this error?
- what is the schema for the collections with the error (as in, what does sqlGetSchema return)?
Regards,
Tarun