Your best bet is to e-mail support immediately for quickest response  and have some documentation of trying  to get a resolution to a problem that should be covered  under the 1 year  warranty, even if it takes longer than 20 days to get problem resolved or the tablet swapped out. 

Any issue, contact support@autel.com. We will help you via Email.

If it can't boot up at all, I am afraid it is hardware issue. Please contact your seller directly to arrange for the repairing.

I definitely would get a certificate of mailing, insure it, and get delivery confirmation. If it is being shipped back to the retailer you need to follow their return instructions and they probably should send you a shipping label. Hope all works out, and Autel give you a reasonable window of time to update it to current level.
  Kinda would suck if they shipped you a new unit that boots up , but you can't register it and have authorization to  access the diagnostic software because you are a little  past your expiration.