I had the same problem today.
Reamped some guitars yesterday for a client, and everything worked fine!
Today i was going to reamp another session and all of a sudden, no input. All of the inputs appear to be dead. But the profiler itself seems to work pretty fine.
But without an input my Kemper is only an expensive box filled with leds and pots that does nothing...useless!
I contacted the support service and they where super-fine and fast.
But I'm about to cry just because i have to rent a Kemper from someone just to keep on working. 