It's difficult to say exactly how to repair a Radeon RX 460 without more information, but there are a few steps you can try that may help:
# Make sure that the cables connecting your monitor to your graphics card are securely plugged in at both ends.
# Try unplugging the power cables from your computer and plugging them back in to reset the hardware.
# Check the settings on your monitor to make sure it is set to the correct input source (HDMI, DisplayPort, etc.)
# If your graphics card has a separate power cable, make sure it is securely plugged in.
If these steps don't help, it's possible that your graphics card has failed and will need to be replaced.