For some reason now when i try to do the alt glitch it does not work. Does anybody know a fix?

Did you make sure your window is selected ?

Sorry but what do you mean by window is selected?

Are you using the correct version (ogversion)? Alt won't work in 1.2.5

For example, if your game is running but you're on your browser, when you alt, it will alt on your browser. Not in the game.

Alt works on 1.2.5, you can even do the ceiling clip. It works differently but it works.

For some reason it only works sometimes and sometimes it just stops working, and yes I do the glitch when I'm in the game window

Sorry but I know why it wasn't working, sometimes my keyboard switches it's layout and on some layouts the alt key doesn't work as intended.