My best advice for anyone using Pro Tools First is; don't use Pro Tools First(it just isn't good due to its many limitations and shortcomings)
Now, I'm not sure if it is the cause of this issue, but a good way to check is to remove it and get the free 30 day trial of the full Pro Tools software.
Having said that, according to the main Avid website, PTF SHOULD be able to run 96K, so that leaves 2 other possibilities:
#1-the interface doesn't support 96K, or is defective
#2-some other program(or the OS) is using the interface and locking PT out of controlling the sample rate(to fix this, try setting the computer to use Core Audio or the on-board audio, to free up the interface for total control from PT)