invalid prefix $10 note BFR

I have a 10 that I am trying to enter. Serial number prefix is BFR. I keep getting an error message that it is an invalid prefix. Does anybody know why this is happening?

It has not yet been entered in the system..Scan it and send the scan to admin..

It has not yet been entered in the system..Scan it and send the scan to admin..Click help at the the top of this page and then on contact us….