For any prop firm registered as a BD (including T3, Hold Bros, Chimera), the licensing requirement is the S57 as of January 1st, 2016. The only exception to this requirement is if you were previously registered as a prop trader with a S7/55 combo or S56 and thus grandfathered in.
If you do not have an active 55 to go with your 7, you may have to take a test.