Amp will not power off

Hey folks,

I have owned a Forte 1A class A 50 wpc SS amp for several years that has been working great until a few days ago.

I have used a Bryston BP26 preamp with it for a while until about a month ago when I bought a hybrid tube preamp (Black Ice Audio F360).

The F360 has been used quite frequently during this month.

A few days ago, a friend brought over a Melos tube preamp. We hooked things up and listened for a few hours.

After listening for the evening, I flipped the power switch on the Forte 1A to the off position but the LED stayed on and the amp did not power down. 

Waited a while. Then tried toggling the switch a few times but eventually had to just pull the plug from the power supply.

Anyone experience this? Hope it's nothing serious.

Thanks!