I have a Jimi Hendrix Dunlop Wah and I'm getting no volume from it when its on. If I switch it to off everything works fine but nothing gets through when its on. Everything is plugged in properly and I've tried using batteries and ac power.
Fender Highway One Stratocaster
Seagull S6+Cedar
Yamaha Pacifica
Epiphone Valve Special
Boss OD-3
Boss DS-1
Dunlop Jimi Hendrix Wah
It's kinda hard to tell on this kind of thing without taking it apart. I'd recommend doing that, and looking at the internals for anything that looks loose or broken.
MG Free At Last
I had a gcb 95 and it did that when there was no power. So I know you said everything is well plugged but you could check the power alimentation.