According to [this manual](https://community.denodo.com/docs/html/browse/7.0/vdp/vql/appendix/syntax_of_condition_functions/analytic_functions_window_functions#analytic-functions-window-functions), Denodo supports Analytic Functions such as RANK function means that it can delegate to the data source, not execute it. In other words, if something blocks the delegation of the query including Analytic Functions entirely to a data source, I will get this error. In order to confirm if the query is delegated to the underlying data source, I would check [Execution Trace](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/appendix/execution_trace_information/execution_trace_information#execution-trace-information).
I found the relevant info in the following manuals. I believe these should be helpful to you.
* [Data Source Configuration Properties](https://community.denodo.com/docs/html/browse/7.0/vdp/vql/generating_wrappers_and_data_sources/creating_data_sources/data_source_configuration_properties)
* [Analytic Functions(Window Function)](https://community.denodo.com/docs/html/browse/7.0/vdp/vql/appendix/syntax_of_condition_functions/analytic_functions_window_functions#analytic-functions-window-functions)
If the issue persists and you are a valid support user, you may open a Support Case at the [Denodo Support Site](https://support.denodo.com/) and Support Team will help you.
Hope this helps!