Need Help with my Proceed AMP3

My AMP-3 has been working perfectly for more than 10 years.

Recently, something has gone wrong. It can still work but cannot be switched off by the power button.

I opened the case and found those red LEDs on the circuit boards are always ON. Pressing the power button has no effect on them.

Any ideas how this can be fixed.

Any suggestions would be most appreciated.

KK