Fire red cheat codes either do nothing or freeze the game

If you're on an emulator, check its own cheat menu wants the code in the right format. Some want the code split over lines exactly as written, and a missing line break is enough for it to do nothing. And turn off any code you're not using, two codes touching the same thing is a classic freeze.

Usually one of three things. 1. Game version. FireRed has a 1.0 and a 1.1 release and a lot of codes only work on one of them. 2. Code type. GameShark and CodeBreaker codes aren't interchangeable. Paste one in as the other and it either does nothing or crashes. 3. Master code. Many code lists start with one that has to go in first. Add one code at a time, and do a proper in-game save (not a save state) before you try anything. Walk-through-walls style codes also freeze if you leave them on during a cutscene, so turn them off when you're done.