Trouble with power locks on K12

Hello everybody. So, one of my passenger power door locks does not operate properly when the car is locked/unlocked. The lock does not respond when the button to lock the doors is pressed either. Any ideas what might be wrong with my power lock on only one of my doors? As far as I know, the door has not been worked on, and when I checked out the cabling today, I didn't notice any fraying or loose connections.
The power window works on said door, and the manual (mechanical) lock button on the door works just fine. I'm driving a 2003 March (K12). Thanks!
I'd imagine the latch mechanism has failed - changed one on my Smart the other day, it wouldn't let the door close, then started working again but the door registered as open, so I couldn't lock the car and had to drive with the warning.

Replaced the latch (£77 and 90 mins) and all is well.

It's likely easier to change on the K12 too - on the smart you have no interior door cards, and have to remove the OUTSIDE door panel, which is a pig of a job, and most of the time was putting that back on straight.
Well in my k12 that botton is just to know if is locked or not, I locked with the intellykey
1.- Gettin the car
2.- Push the brake
3.- Check the Key advisor is in green
3.- Push the Lock in the remote control
4.- And is ready

It is only to no one in the outdoors can open the car when you are driving

Keep in mind that any one in the interior of the car can open any door, and after that all the doors are unlocked (so if you have kids-use the kids-secure lock)