Please, always include the model and year of aircraft when asking questions. There are too many differences with models.
Check all the micro switches and wires that energize the switch, on the doors and the uplock switches. Doors will not close if the system gets a signal that the gear is not up. If one of these wires is broken, loose or not making contact the doors will not close. Also if the switch is not making contact to the strike area then the doors will not close. It is a closed system and if one switch is open or wire is not connected that will cause the problem.
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