Musicman Majesty no sound / problem

Hi my musicman majestyc 7 string have no sound. Only if I unplug the cable, plug it back in and hold down the piezo volume knob I have sound until i let off of it. I already tried the 10 second hold, change baterries and all that stuff and only have sound if i hold the piezo knob. I dont know what more i can do. I boght the guitar in guitarcenter on manhattan almost 3 years ago in march 2017, and I from argentina i dont know what to do 🙁 very dissapointing and disgusting situation for thjis kind of guitar.

Sorry for the mistakes. I speak spanish.