Can't zoom in GMod anymore...

Well, anything that’s supposed to let me zoom doesn’t work anymore, every overlays of guns works but it just doesn’t change my FoV…

I know it’s my client, but I don’t know what’s causing it.

Go into options and assign a key to suit zoom if you haven’t already.
If you mean like looking through gun sights, it’s right click. find a way to bind that in console or something. sorry I couldn’t be more helpful.