A French Door with the Latch Sticking at the Bottom
If the latch is getting stuck, even if you try to engage it when the door is open, then the issue is a problem with the latch itself. The latch has moving parts, which undergo wear and tear as it is used. Lubricating the moving parts might help with the sticking issues, but in some cases the latch will still not work properly. Normal wear and tear eventually causes a latch to become non-functional. The easiest way to deal with latch issues is to replace the latch entirely.