Classé CA-400 - Unresponsive - Let's Bring It Back

On Black Friday at my Best Buy a customer brought this amp in to recycle. I was able to talk them out of this and to give me the amp to attempt to revive. I have no experience in this field, but based on the symptoms I am hoping it is something simple. If not, I will learn a lot along the way.

Presently the amplifier shows no sign of life. I visually checked the ceramic fuse on the rear it looks ok. I also opened the top panel to make a quick visual inspection and don't see any bulging caps or signs of thermal events. I have ordered a multi-meter from Amazon which will arrive tomorrow. I plan to spend more time this weekend with it and appreciate any advice from the community.

I have read this thread but the symptoms are much different.
 
Just an update. The issue appears to have been an easy fix. The mechanical button on the front was misbehaving. I disassembled the front plate and removed the button. It appears to be good as new. Awaiting some spade to banana plug adapters and will report back.
 
Yes a lot of electronics goes to landfill or "recycling" because people don't know where to take them to get a diagnostic assessment, or it costs a small fortune to get it tested...

my kids iPad got stuck in a boot loop and the Apple tech, after being unable to unable to bruteforce an IOS re-installation, said that the "only solution was to buy another"...

luckily most of these amps from the 20th Century can be repaired.

I found out the hard way that there's no repair/service available for a Hypex amplifier. Not even a return to base option for diagnostics for a UcD400MP...