Oracle 12.1.0.2 SE-2
SQL Dev 18.3.0.277
So, while I'm not a complete stranger to creating user-defined reports, it's not something I do a lot of.
I create a report:

And when I try to run it

So I would like to buy a clue as to what it thinks is missing or invalid. The exact same script, pasted into a SQL Dev worksheet, performs perfectly.
Ok, so on a guess I commented out the SET, COL, and BREAK commands. Now the report runs, but of course without any of the formatting I intended. Am I overlooking something, or expecting what really isn't there?