Super unfortunate.
Despite the transfer of the email address and license code via message on Discord as requested, it seems the developer doesn’t care about their customers at all.
Appsumo should maybe gradually consider setting the refund period to 365 days or even lifetime, especially when many providers deceive us Sumolings, restrict access, etc. after such a short time...
Unless Sumolings are just a cash cow for both sides.

In any case, Appsumo's intervention is required here. Regardless of whether the refund period is over.

Or it's about time to take legal action, because even after a refund period, there are applicable laws, and these apply to Appsumo as well as to the software owner!