I have an X1E and I also have this issue. The wiring is different on the X1E than the X1C and I was sent the wrong switch by Bambu. Therefore, I’ve had to use the same wiring form the bad switch by reconnecting them to the new switch. Re assembling today and hope this fixes my issue.
I also have an X1E and am having the same issue. One way to test whether the switch on the power unit is the problem is to push the switch to the ON position while the unit is on, then press a little harder on the ON side of the switch. If the light flashes and it sounds like a contactor, the switch is bad. If it is bad, you could bypass the switch like I did. I’ll replace it once the one I ordered comes in, but this is only a temporary fix.