Cannot communicate with VEX Cortex SlaveCPU

Hello,
When compiling code to our robot we get the following error: “Cannot communicate with VEX Cortex SlaveCPU. Master CPU communication is working.
**
Things I have tried:**
-Manually updating firmware on controller+cortex
-Updating VEXNet keys
-Using a serial cable
-Using a USB A to A cable
-Bootloading cortex+controller
-Using a different computer
-Manually updating RobotC
-Resetting the cortex with config button

This error is really stubborn! Any help would be greatly appreciated.
error.PNG

Usually this means the RobotC firmware is not loaded onto the cortex. Do a software inspection (robot menu->advanced) and post the results. cortex firmware should be at 4.25, and RobotC firmware at 1055 if you are using the latest version.