Hey guys, I have the v3 and after couple years, it finally crapped out on me today.
Don't know if you got this figured out, but for others also, the problem was the power cord. I hadn't used it in a while, plugged it in and my V would get hotter and hotter past the value I set for it. The first time I thought the display was malfunctioning until it started beeping and it certainly was overheating.
So I unplugged it, and tried a few quick things without luck. THEN, I decided to try another power adapter (the one for a Vapir NO2 actually), which is only rated as 13V 1.5A. Then magically it came alive and worked. It heated slower, not surprisingly because the normal adapter is 19V 3.5A.
Then, I knew my V-Tower was "working". I swapped out the extension cord that leads up to the power brick and the vaporizer was back to working... Was it the cord? Was it a glitched reset by the other power adapter? Who knows. I took electronics, so I knew there was some risk, but going lower in voltage seemed a lot safer. I already put away the other cord. Not sure how that could really matter, but maybe this story will help someone.
In short, try a new adapter before throwing your V-Tower in the dumpster!