IS300 no sound from stereo - head unit volume knob/tuning knob not responding (replaced amp)

[HussPatz]

So a few months ago volume knob started acting up where turning the knob did nothing. Then the tuning knob when I pressed on it did nothing. Then there is no sound when I turn on the head unit. I didn't use the head unit for a few months and I replaced the amp today and sound and everything was working for about 30 mins until I turned off the car got back in an hour so later and the same issues came up in the order above. Would really appreciate so advice as to what step I should take next.