If your garage door is of the swing type check that everything is tight and secure on the spring plates.
Garage door not closing flush.
One sends a beam of infra red light to the other.
There are usually two springs on each side of the garage door to swing it up.
There is about a 1 1 2 gap.
The door closes flush to the bottom of the floor.
Garage floor may have cracked or shifted 2.
Depending on the brand.
First check the sensor lights.
Clutter or obstructions that block the sensor are the first problems to look for if your door won t close or in extreme cases open at all.
If you need to change their tensions move them to a new hole.
The reasons your garage door has a gap in it could be.
I removed the sleds and the garage door opener arm so that i could see if those were inhibiting its closing all the way.
With these removed it will close another 1 2 or so but there is still a gap.
Garage door opener malfunction or door has shifted.
First you need to see what has caused this to happen.
If anything interrupts this beam of light the garage door will not close and the ceiling light on the opener mechanism will flash as mentioned in the previous step.
The top however is not flush against the frame.
Garage door seal may be damaged 4.
Garage door sensors may not be aligned correctly 3.