Yamaha RX-V375 distorted sound problem

So I'm having this issue on my old yamaha receiver, has been in storage for a while and I get nothing but distorted sound from all speakers, have also tried other speakers to no avail. Everytime I try to also do auto speaker setup it gives the error that no speakers are connected which makes no sense when you can clearly hear sound in video. I have tried all types of connections from coaxial, hdmi, and optical and get the same results no matter if I'm running the PC, TV, consoles or just the radio. I'm stumped as what to do, have gone through all settings and everything seems right, even thought about a firmware update but of course the unit is discontinued and cant find an update anywhere. Any suggestions would be greatly appreciated.