I only use the avast free version, so I don't know if this might help.
If you log-on to your my.avast.com account, You should see the devices that you have installed, linked to this account. There would also be I believe a record of what licenses are assigned to these devices in the my.avast.com account. Hopefully that should show which licenses are in use and on what devices, this may aid the process of elimination.