Seems that i have the same problem here.
What i did until now
Just purchased a license
Created a my.eset.com account
added the license
reinstalled ESET NOD32 Antivirus for Linux Desktop
during installation entered my my.eset.com credentials
==> When i want to update the signature database i get an "invalid username/password" error
==> in my.eset.com in the license section "activated" is still on 0
Hope you can help me with that!
thx & BR, Alois