I've recently purchased an RX 480 and I'm having an issue where the fan won't turn on at times. As you can see from the image below. No RPM value even at 90 C. Last night I also had an issue where no image was being sent to the monitor and was forced to shut down the PC.
My current setup -
ASUS ROG STRIX Radeon Rx 480 8GB
XFX PRO 550W Power Supply
Latest Crimson Drivers 17.3.1
Windows 10 Pro