So I teach a robotics class using VEX and ROBOTC, and I have an unusual problem. Today, one of the group’s cortexes started refusing to return a complete range of values for analog sensors. It doesn’t seem to be a problem with the sensors, I tried multiple ones. Right now, the pot returns a value from 0 to 98, but it doesn’t seem to be a mechanical issue. It still rotates normally. The light sensor seems to go from 0 to about 150, though I didn’t check this one as closely. I tried redownloading the firmware and everything else I can think of and nothing is working. Anyone have any ideas on what I can do to fix it?
Have you tried those same sensors on a different analog port?
On what display are you observing the outputs?
If you have a multimeter, you can check the pot by connecting the leads and observing the changes in resistance.
I will check the other analog ports tomorrow.
I am observing the outputs on the sensor debug window of ROBOTC.
Good idea on the multimeter, I will give that a try, but the problem seems to be happening regardless of the pot attached, I tried three different ones.
Is the main battery charged and turned on?
I think also that the problem is the cortex is off or battery disconnected.
At least for the potentiometer because I’ve been there too. 
That was definitely it, the battery just needed to be charged. I feel stupid for it being such an obvious mistake. Oh well, at least now I know and I won’t make that mistake again. Thanks everyone for the help.