Please, which FF version do you already have and what version are you trying to upgrade to ?
Which browser are you using ?
Have you tried to use another different browser ?
can you please, explain when this happens, and if possible put a screenshot where this message appears ?
I have already been trying to know the price of the upgrade and it works right, just fill the information needed and sel ect your version of FF to upgrade to and click on submit.
Be aware that the serial number fr om your version must match the version you are trying to upgrade to (basic, standard or pro)
Does your upgrade form look like this here below? Where do you find the problem ?