Apple says the issue may stem from having an inactive SIM with the same number as your active SIM. To fix it, remove the ...
While it was initially believed that the No Data Wipe update had reached devices running Beta 3.1, that hasn't been the case.
Swap the cable to another device to see if the cable or device is faulty. Inspect the HDMI for frays or exposed wires; braided cables resist damage better.