Hmm I'm not sure why it says no queries running. Is the long running query a workflow? If not, what type of query is it (Javascript, Postgres, etc)? If you can share, a screenshot could be helpful. What query type is the data source for the table (Javascript transformer, Javascript query, Postgres, Rest api, etc)?
While we troubleshoot this, you could put the table inside a container component and check on "Hoist loading state" in the container config - that should show a loader to end users while any queries are running. Another option is to put some custom logic in the container's loading setting to show a loader while certain queries are running:
At the bottom of the screen, you can open the Debug panel to view the console. There, you can see which queries are running successfully and which ones are encountering errors.
As @Tess mentioned, you can also set loading states in your app accordingly.