I have come across the same issue when I mistakenly use the Microsoft SQL Server adapter for the Azure SQL Data Warehouse data source. After using the correct adapter(i.e., Azure SQL Data Warehouse) the above error is resolved.
To analyze the root cause, I would modify the Virtual DataPort log level as “Debug’’ in **<DENODO_HOME>/conf/vdp/log4j2** and check for the possible causes in the vdp.log file in** <DENODO_HOME>/logs/vdp**.
For more information, you could refer to the section [Log Configuration](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/appendix/configuring_the_logging_engine/configuring_the_logging_engine) of the Virtual DataPort Administration Guide.
If you are a user with valid support access and still facing any error, I would suggest you raise a support case in the [Denodo Support Site](https://support.denodo.com/).
Hope this helps!