I Know that beta 2 requires a different key to beta 1 maybe the extension keys for beta 2 are not available yet, beta2 does at least have a 60 day trail period. So I wouldn't be to concerned for the moment.
If you send me your FB4 extension key under separate cover (private forum message), I can check whether it's a Beta 1 or a Beta 2 number.
Just to close the loop...
Fb Beta 2 accepted the license number. I'm not sure where I went wrong (I had both beta 1 and beta 2 installed, requested a key, and thought I was entereing it in beta 2 - though possible I got my wires crossed (?)).
After uninstalling Beta1 (for unrelated reasons) my Beta2 key worked just fine. Not clear if it worked because I was entering it in the wrong app in the first place (don't think I was but...), or if uninstalling Beta1 had something to do with it.
All's well now though.