Doors and Windows - Door won't close

I have an all-wooden door between the garage and family room that just recently will not close. The latch does not catch which leaves a 1/2 - 3/4 inch space where cold air drafts in from the garage. Any input on what the cause might be and how to correct it would be appreciated. I've checked to make sure that nothing is loose. Door has worked fine for the past 4-5 years.

Thanks.

Couple things here; the door has worked fine and it not closing now, maybe the door expanded as the weather got cooler.

You can plane the edges of the door where it is stoping it from closing, but keep in mind that once the weather starts to warm-up, the amount that you plane off will now become a gap when your door is close.

Before planing the door, check to see if the hinge side of the door is not coming loose and needs to be screwed back to the jam tightly.

If that's fine, then go ahead and plane the door edge and apply two coats of penetral to the cut edge. this will seal the door from expending futher.