Support Ticket Refund - https://support.avast.com/support/tickets/new?form=2.
Complete the support ticket and wait, don’t submit multiple tickets as that slows the process. They are handled in a first in first out, so multiple ticket would be combined and go to the end of the list.
Currently completion is damn slow up to 15 business days. This shouldn’t stop you getting a refund provided you are entitled, e.g. submission before the end of the refund period.