[Elecraft] KPA500 was working now it’s not

[vtnn43e at comcast.net]

Powered up my KPA500 today for the first time today and it was working ok with my Flex-5000. Got 500 watts out on 40 to a dummy load and everything seemed ok. Powered the rig and amp off then on and all of a sudden get only 35 watts out for 35 in. Does not matter what band I Put my rig on as I only get out what I put in. Don’t see any errors and the amp is in OPER. There are no faults BTW. 

Anyone have any thoughts as to why I no longer get any output from the amp? 

Zack 

N8FNR