Hi @gromani and welcome to the community!
That “Allow Q&A on data” checkbox only enables through the second option, “Use a linked topic for Build Visual and Q&A,” not “Use datasets.” Once you select a topic there and hit Apply Changes, the box checks itself. So what you’re seeing on the “Use datasets” side is expected, not a bug. Here’s a related community post about this: Cannot Enable Dashboard Q&A when publishing - #2 by Brett .
A few questions to narrow it down: Are you an owner (not just viewer) of the Topic and all three datasets behind it, since linking fails if ownership is missing on any of them? Had the Topic fully finished building and indexing before you tried, or was it still processing? And does it still error after a page refresh or fresh browser session, since the publish dialog can hold a stale state after you switch between the two Q&A options? Once we get those answers, we can provide more tailored assistance.
Hope this helps and please feel free to keep us updated!