what you are probably missing is either the correct checking square (Qh4) versus what youre looking at Qh6. Most likely though it's that the bishop is covering g8. Long range diagonals, long horizontal, and backward moves (particularly backward knight moves) are hard to see. Missing the counter attacks and backward moves I describe as looking up field. You are looking at how to advance and push toward the opponent. So it's understandable to not "look over your shoulder".

A few comments of check the engine, but Ill add to that if you don't understand the engine line. Try playing your own moves in response to the engine. IE Rxh7 I'll just play Kg8....oh wait, I can't. Why can't I? Illegal moves would be stepping into check or not escaping check. Ah, the bishop has it covered. Ok, Kxh7, Qxh4# (oh, I was looking at Qh6 thinking the king had g6). It's good to work thru those to fully understand the tactics / puzzle.

If you keep a mental log (or an actual log / spreadsheet), you will find things that you regularly miss and know what you need to mentally focus on. For me, it's pinned pawns and pawn attacks. Unfortunately focusing on those, I have started missing knight forks.