I had this exact same problem. I paid for Membership, but Sonar wouldn't recognize it and kept asking me to join. When I pushed the button to join, it would tell me I'm already a member, putting me through a vicious loop. However, something finally occurred to me:
When I initially signed in, I used my original username and password. During the upgrade process, I was asked to create a "Profile" name and password, which I assumed would be separate and used only for online file sharing, etc. However, after trying every method I could think of, I finally logged out of Bandlab, then logged back in with the new Profile name and password, and this worked. Membership was recognized, and I was able to download all the new features.
Hope this helps.
