On the IDSMC, I added a 4.X sensor. Then I navigated to the signatures selection with the sensor as my object. For some reason the signatures listed were blank. All I saw was this:
General 0 of 0
Custom 0 of 0
I tried to upgrade the director and sensor to S42 (they were at S37) to see if the signatures appeared there, but they did not. When I connected a 3.X sensor the signatures showed up fine.