Yes, that's right - DX5 doesn't appear. It is cold to the touch whereas before it would always be very warm. I'll have to use my built-in monitor speakers until topping can fix and return it which will make my ears bleedI understand your situation.
Then, even if you check the audio device from the Windows control panel of the PC, there is no indication of Topping USB DAC there, right?
In that case, DX5 itself may be broken.
(By the way, Topping's latest driver is V5.30.)