PS Audio BHK300 didn’t work this morning.

I would also try shutting it down and unplugging it from the wall for 5 minutes.  Unlikely to help but worth a try.  I would have thought a blown tube, but in standby the tube is off so likely not that. 

@OP PS Audio specifically say to unplug the unit from the wall if it goes into protection mode and won't reset.

I am surprised, if there is an internal problem, that the blue on off light is not flashing.

Since you have changed the fuse - having done the above - if still no sound, I would recommend checking all the fuses again with continuity tester.

If one has blown again it suggests and internal fault is definitely present.

Sorry to hear of your dilemma, unfortunately I can’t offer any help. But I wanted to share an experience I had about 2 months ago. I have a pair of 55# tube mono blocs and one had a failure. I called customer support ( Rogue ) and was advised to ship it to them for diagnosis and repair. They recommend “ Pirate Ship “ to obtain shipping labels and insurance. Second I decided to send both amps for a checkup and found out that the “ Bridge Rectifiers “ in both were tired and needed TLC in addition to the issue I had noted. I apologize if I have insulted your intelligence, but just wanted to share my experience in case it might help you with your issue. Respectfully, Mike B. BTW you have a fabulous system. 

@viridian 

Yes. And I reversed the input cables, checked the source and preamp. 

@mattmiller 

They just got back to me today and are going to send me a RMA so I can send it in.