Is your serial number exactly 24 characters long? Also, did you buy the boxed version from big resellers like Amazon? Please answer these questions BUT don't post your serial number here. This is a public forum and serial numbers are your private property and you should look after them securely.
It could be that you have what is called a Redemption Code. If this is the case then try this link and follow the instructions to get 24 characters Serial number:
I am based in the UK and we don't have B&H photo so I know nothing about them.
What isn’t working? A serial number is 24-digits.
Did you buy a box or a download from B&H?
For reference here is the B&H boxed item:
And here is the B&H download item: