Whilst this is a pain for you you have up to 30 days unrestricted use to get this resolved.
Did you check that an anti-spam isn’t involved, though not finding a record when you used the resend license, would probably rule out any anti-spam involvement.
Did you purchase via an avast reseller as asked or directly via the avast.com site ?
I think this is on-line payment is still handled by Digital River Element 5 (but I’m not sure) - you could also try contacting them.