I have a new M1 Macbook Pro with Monterey 12.3.1, and a new 2TB X5 SSD, which I bought last year, but am using for the first time. the model number is MU-PB2T0B.
When I plug it in using a Thunderbolt cable to a Thunderbolt port on the laptop, the activity light on the X5 comes on and off, showing that it is connected. The drive does not appear on the desktop and when I run Disk Utility it does not appear there either. Looking in System Report all three Thunderbolt busses, 0, 1, and 2, say "no device connected".
The X5 gets warm after a few minutes, suggesting activity.
Any help gratefully received. I bought this for top dollar as the best available SSD and I am eager to get it into use.