Can't use Temp Tables - really?

Is it possible you're using mixed storage modes (both Import and direct query) in your report?  In my experience using mixed (I use powerapps for direct query), even the tables I am actually just importing have the "direct query" radio button defaulted for some reason.  If so, switch the button back to 'import' and you should no longer have the problem.  I just tried it my issue (which is how i got to this forum) and it worked great.  The reason is that Direct Queries are super limited in what they can pull.