I already did that, but the computer that was the orignal primary computer has Multiplicity V4, beta 2 on it, and the new computer that is the new primary computer, is just Multiplicity 4, and if I want the Beta on there, I would have to repay for it again.
You license will be good for all versions of Multiplicity 4 (betas and releases).
Multiplicity 4 is now out of beta so you won't find that version anywhere unless you have an old installer.
It is possible the your license key and email address aren't matching up (they both do need to match correctly in order to activate). Did you have a different email address used when you purchased the beta?