Query returning error in Premium Data Tables

I have written a query with sub-queries. When testing in the Query Builder, it executes and returns data as it should. However, if I try to use it as a Custom Query on a Premium Data Table (I have it licensed) it simply returns the terse message ‘ERROR: invalid query’. I tried the same query on the MySQL command line and it also works. Are there some limitations in place as to the kind of queries that are allowed in Data Tables? Or is there a way to get a more detailed message?

This application isn’t published yet. I can provide the SQL block if necessary. I also presented this problem as a comment in the https://wpdataaccess.com/docs/query-builder/writing-queries web page – sorry for the duplication. I tried to submit a ticket through Premium Support, but was unable to do it – since I only have a local URL for development, the interface does not accept it.