if youre able to find other variables in the game (like money or health or whatever) and changing them actually works, then you're definitely attached to the correct process and either one of two things are happening.

1: the game got updated and the aob no longer exists in the game's code (this happens all the time with multiplayer games)

2: you're not searching for the AOB correctly. make sure in cheat engine the value type is set to array of bytes, the hex checkbox next to the search is checked, and you might need check the "writable" box so its a grey/black square

Thanks for your answers. However, I still can't get it to find the string (I meant using already known AoB hacks).
I am doing things the way thenewcomer described in #2, and I am looking for the "before" string, just in case there is any doubt :P

Could it be the browser? Can you confirm that you find the one posted here for Bit Blast in Chrome?

Just to clarify again, I can find and change variables myself, and I can search for an AoB like something silly (idk, maybe 63 ??) and it returns something, but none of the AoB I tried for any games are found.
 

I do Shift + Esc and it's pretty straight forward to find the process: it's the one that appears when I enable flash, and hangs directly under the game tab.

It is a chrome thing, at least for me. I tried it in firefox and it worked :) The big hitbox mode is really nice! I already had everything maxed and achieved without hacks, but it is a nice mode :)

Thanks for your time!