The latch is likely not entering the striker plate's recess due to a misalignment issue. The door could have drooped slightly, so first, check that the hinge screws are tightened correctly. To determine the issue, close the door and carefully examine where the latch meets the striker plate.
This is a major security risk because when the lock isn't hitting the strike plate, it simply can't close properly, and it can be caused by a number of issues. Damp weather can be one of the reasons behind this misalignment with the strike plate, as well as if the lock wasn't properly installed.
Loosen the screws a little, and see if the latch operates as it's supposed to. If it does, just gently tighten the screws, checking to make sure the latch is still operating. If not, you will probably need to replace the lockset; they don't repair easily.
The most likely cause is that the latch isn't engaging properly with the strike plate – the two crucial parts that need to interact in order for the door to stay closed. You'll generally be able to tell by the absence of any clicks or snaps when you push the door closed.
Try Tightening the Screws
If you suspect there's an issue with your door hinge, use a screwdriver to tighten any loose screws before making other changes. If the screws turn without tightening, you might need to use longer screws. This can be useful for fixing a sagging door, too.
One of the most common reasons people find their door isn't locking is because of a misaligned door. Whether it's because of the door itself on the hinges, how it fits in the frame, the striking plate or the location of the lock, a misalignment can mean your door won't lock properly.
If the latch won't retract by use of the knob or handle either, then you should check the spindle and the latch mechanism to make sure they are still connected correctly. If neither of these will close the latch, then it is either broken or damaged. Examine the condition of the latch for any obvious defects.
Factors like the weather, damage to the key, and even a buildup of dirt and grime inside the locking mechanism can all stop a door from locking. If you're having trouble locking your front door on a regular basis, you should consult a locksmith as soon as possible.
To try and fix a door latch stuck within a door, use a flathead screwdriver or a Philips head screwdriver to free the latch. Open the door and hold it in an open position with a door wedge. Next, place the screwdriver at the top of the latch and use a hammer to tap the latch and remove any obstructions gently.
This is typically a small button or hole on the side or bottom of the lock. If your lock has a reset button, press and hold it down. For locks with a reset slot, insert the reset tool provided with the lock. While holding the reset button or tool, set your new combination by turning the dials to your desired numbers.
If you can turn the key but the lock isn't turning it is probably because there is an issue with the lock's mechanism system. In cases like these, the lock may need to be removed or replaced.
Door lock problems are often caused by a malfunctioning lock mechanism or latch assembly, but there are several common reasons why locks stop working: The lock is dry or dirty. It doesn't fit in the door properly. The latch and strike plate don't align.
Begin by inspecting the lock and the key for visible signs of damage or debris. If dirt or debris is present, use a lock lubricant spray or compressed air to clean the lock cylinder. Insert the key and gently wiggle it to help dislodge any particles. Avoid using excessive force, as this can cause further damage.
If lubrication helps the lock work easier, but you still feel resistance when you turn the key, you should try using graphite powder in the keyhole. If it's still not smooth and catching you may need to replace the mechanism or cylinder.
Often, a door not closing properly is a hinge issue. Grab a screwdriver and tighten those screws on both the door and the frame. If the screw holes are feeling a bit loose, consider using longer screws, such as 2-3" screws or inserting wooden dowels (or even some wooden toothpicks) for a sturdier fix.
There are many reasons why a door won't latch. Most of the time, it's because of old hinges causing a sagging door—or the door wasn't installed properly in the first place. For example, the door latch may not be perfectly aligned with the striker plate. Or there could be an issue with the door jambs.
Dirt and dust can sometimes find its way into a lock and build up over time. This can clog up the locking mechanism making it difficult to turn. You can apply some graphite spay or silicone based lubricant in the lock, put the key back in and turn it a few times.
Moisture inside the lock can freeze if temperatures drop low enough.
De-Ice the Keyhole – The best option is to use a de-icing spray to target the keyhole of the lock If you have access to a lubricant spray, such as WD40, this can also be used to clear some of the ice from inside the lock cylinder through the keyhole.