Okay here is how I would tackle this:
There is a chain of components that spans from the flight controller all the way down to your motors.
We need to isolate each component and determine where the breakdown is.
The first thing I would check is my cabling, especially the ones I made myself. Do the pins on one side of the FC-ESC harness have continuity with their corresponding pins on the other? Do you have any pins that have continuity that shouldn’t? Once you are confident about your wiring, head to the next step.
Now lets check that the cables are plugged into the right place. Does esc output 1 connect to motor input 1 on the ESC? Do this for all connections.
If you still get 3/4 spinning, start swapping the FC to ESC ordering (plug the non-functioning motor into a known functioning motor’s port). Does the motor now spin? If it does, odds are you have a bad wire or connection (or potentially broken channel on your ESC but while this IS possible, its not likely). If it still doesn’t spin, you can rule out the FC from the chain and work your way down.
I would then swap the motor outputs. Again, put a non-functioning motor on a functioning motors output and see if it spins. If it does then you can rule the motor out, and focus your efforts on your ESC and wiring.
That being said, I’d like to avoid dog piling on one support thread. While its possible you may have the same issue as OP, its likely that your situation is slightly different and so you should make your own thread so we can support your specific case. That being said if you’re all from the same team, and therefore dealing with the issue on the same drone, feel free to chime in on the same thread.