It sounds as if the power amp or perhaps a power supply has packed up on ya. If you've double checked all the power output settings to make sure the amp is enabled then you need to find someone who is handy with electronics repair to take a look at it for ya. If both channels are dead it's more likely a power supply issue of some kind which is typically the most failure prone part of most electronics.
I would not bother with a so called authorized Line 6 repair shop because most of those folks are just PC board swappers. Since Line 6 has decided not to continue support of the Vetta you're pretty much on your own.
This is why I don't recommend that anyone buy a Vetta unless they are either an electronics tech or engineer that has the test equipment, can read a schematic and is also capable of component level electronics repair.
It's most likely fixable but the only real problem is finding someone who can actually fix it. While the PC boards are no longer available from Line6, the component parts are from the usual electronics parts distributors such as DigiKey and the like.