Recently I have discovered a very strange bug where, turning on the controller while the DSX is enabled... It will cause the controller to not be 'detected' by the software.
I'm using built-in PC Bluetooth receiver (no external Bluetooth receiver)
This bug feels somewhat consistent.
It might be PS4 fault for being terrible, but when I shutdown DSX and open It again.... controller will be detected properly.
There are no other bluetooth devices connected other than PS controllers.