I had a student whose controller power button started blinking red. It will not charge, link to the brain, or connect in VEX IQ software. We have tried multiple cables, we have swapped out fully charged batteries, and I have tried to connect to multiple devices, including a desktop, a chromebook, and my own laptop. No luck on any front.
I contacted VEX directly. and they wanted to replace the battery. I tried that on my own with a different controller battery, and it did not work. After leaving the controller alone for a few weeks, the problem went away, which I know is not a great answer.
I had the same issue and reached out to VEX Support, these were the directions I got from them:
Install the App version of VEX IQ Code If they already have it installed, then good. We basically just need the drivers out of it. Leave the app closed.