I have exactly the same problem.
The old "De-Install, Re-Install and try again" solution doesn't work. (I come from the software industry and it must just be embarrassing for a software company to even have to suggest this - we're in the 21st century, not the 1980s - that answer just means you don't know what you're doing.)
I have tried opening 3 messages with the license Department online since January. 06022014, 06050918 and 06089444. In the last one I set a deadline for reply. It's quite a simple matter for me.
1) This technical licensing issue is not an issue for resolution in a "Forum". "Forums" are just the cheap way in which Software companies fob-off users instead of providing "proper" support.
2) If we are not offered a solution by 19.03.2018, anyone interested in suing Avast, please list yourself here (without any personal details) - then we can then work out how to get in contact with each other once the deadline expires.
I am fed-up of bad support, bad quality and generally being ignored as a customer. I paid for a service which I cannot use and Avast is just ignoring me.
Regards,
John.