Maybe show us the code.
Just checking: Vex IQ? Latest firmware (2.1.3)? Latest RobotC (4.56)? Which Windows version? Laptop?
Tried restarting everything, computer, bot?
Was it working before, and has something been changed since?
You might be helped by this (click the triangle):
Device Manager & drivers...
The driver needed to for Windows to communicate with the Robot Brain is only available inside the VEX IQ Firmware Update Utility installer. You must run this installer before connecting the Robot Brain to your computer. The driver might not correctly install if VEX IQ devices are connected to the computer before or during the installation.
To correct these issues, please follow these instructions:
Physically disconnect all VEX IQ devices from your computer
Uninstall the previous versions of the VEX IQ Firmware Update Utility
Download the latest (version 1.17) of the VEX IQ Firmware Update Utility. Launch the installer. Use Run as Administrator if your Windows user account is not an admin account.
Follow the installation steps and leave all settings as default values. Ensure the Robot Brain is NOT connected during any of this process,
About half way through the setup wizard, a single pop up window will appear that says “The next step will install the necessary drivers for your VEX products.” Click OK to install the VEX USB serial port driver. This is the ONLY popup window that appears during the installation wizard.
When the installer finishes, you can now connect the Robot Brain to your computer and turn it on. Windows should automatically recognize the device as the VEX USB serial port, as indicated by a tiny popup message box in the lower right system tray.
This can be verified in the Device Manager (click Start, type in “Device Manager”, then launch the program with that name from the search results).
Under "Ports (COM & LPT), you should see “VEX USB serial port (COM20)” on your computer. Please note that depending on the computer, you may see a different COM port number. The specific COM port number does not matter as long as it is unique (no other devices on that same COM port).
If you can see “VEX USB serial port” listed here, your computer can now communicate with the Robot Brain.