In order to debug the Custom Wrapper, I would follow the steps mention in the [Denodo Application Debug Configuration](https://community.denodo.com/docs/html/browse/latest/en/denodo4e/reference/debug/denodo_application_debug_configuration/denodo_application_debug_configuration) section of the Denodo4Eclipse Plugin Guide.
I’d also recommend you to read [How to debug Denodo custom extensions with Eclipse](https://community.denodo.com/kb/en/view/document/How%20to%20debug%20Denodo%20custom%20extensions%20with%20Eclipse) Knowledge Base article. I find it very useful to understand how to enable the Debug mode for the Denodo custom extensions.
Along with that, I would also modify the Virtual DataPort log level as “Trace’’ 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/latest/en/vdp/administration/appendix/configuring_the_logging_engine/configuring_the_logging_engine) of the Virtual DataPort Administration Guide.
If you need further assistance and if you are a user with valid support access, then you can raise a support case in Denodo Support Site so that our support team can help you.
Hope this helps!