This is still an issue with the release version of RAdmin Viewer 3.0. It will not transfer a license code to a 2.2 server, though it acts like it does.
For those of you also experiencing this problem: I recommend, at least until Famatech addresses this issue, that you keep a backup copy of the original Radmin 3.0 beta viewer, along with the phone book to go with it. (As I'm sure you know, the beta 2 and release versions of the phonebook are incompatible with the initial 3.0 viewer release.)
If you've lost the original 3.0 beta viewer, I don't believe Famatech has it available for download any more; if you're desperate, send me a PM and I'll e-mail it to you. You're on your own for rebuilding your old phonebook, though.