Why are my car stereo speakers not working?

I m going to try to explain this as best as I can so bear with me.

I have an alpine cde-235bt. It s been installed in my car for over 2 years. Recently, as of one week ago, I run into an issue where I turn on my car and I just have bass from my subwoofer. No sound coming from my stereo speakers. Then other times I turn the car on and everything works fine.

I have 2 kicker door speakers 2 Rockford fosgate door speakers and a 2600 watt boss amp with 10 inch Rockford sub. Nothing crazy just a stable system.

Now I do know that the wiring was messed up by the shop that did the install. At first they ran it to a constant so my battery kept dying. And now, the little scanner module for under the steering wheel does not work because of miswiring.

I have no taken it apart to check their wiring, but my mechanic said that it s wired wrong for sure if it can t be scanned for issues.

I m asking on yahoo before I take it and spend the money to get it looked at. Is the stereo speaker issue because the stereo is dying? Or is it just bad wiring showing after a few years?