p38 door won't lock

i have just bought myself a 1997 range rover p38 and the front passenger side door wont lock with the central locking. i can push the lock down inside and it locks all the doors but when i press the lock button on the key fob it locks the other three door and the tailgate but not tthe front passenger side door i have had the latch out but cant see anything broken can anyone point me in the right direction please

Mine is the same. The motor inside the lock is burned out.

The only thing I'd add is that an enterprising member on here has discovered that it is the same motor in front and rear doors and you can usually pick up a rear lock assembly a lot cheaper than a front one.

ok thanks guys will order another one then