I had experienced something similar. What I did was put a powered USB hub in line with the x-controller. Prior to that, I bypassed the USB header and plugged a cable directly in to the USB port on the controller. Both worked for me. Here is another thread you might want to read.
There are multiple reports of not connecting, or disconnecting part way through a cut. Some have changed out USB cables altogether or even added some ferrite cores.
Not sure if this is the reason you cannot connect but it it worth trying. If this doesn’t work I would suggest searching “x controller not connecting.”