Robot Won't Tether

We have four robotics teams at our school. This is our third year at robotics, we went to Worlds the past two years. I give this background because I feel like I should be able to troubleshoot this myself! That being said, I cannot get one of our robots to tether. Here is what I have tried:

-Updating all components.
-Swapping out radio cards for new ones.
-Trying our new brain and remote.
-Trying an old brain and remote.
-Using different tethers.

Please help!

The very first thing I would check is to make sure the radio is plugged in all the way into the brain.

By “Tether” you mean you can’t connect the remote to the brain with a wire? There should only be three parts, the brain, radio, and cable. Switching those one at a time should tell you which is not working.

If you’re trying to connect them via radio (instead of wire), the same process should work (switching one at a time)