Cause of misaligned patio doors
It doesn't make a lot of sense that there's a gap the entire height of the door. What's preventing it from making contact?

As for the twist, one of two things is likely the culprit:


One or both of the doors is warped, due to excessive moisture and/or prolonged sun exposure. If that's the case, you'll probably just need to use extra force until it dries out. If it doesn't relax, you may need to replace the doors. 
The wall has shifted, or the door frame has shifted in the wall. You'll need to apply some carpentry-foo and reset the door so that it's plumb, level, and square. 


A close examination of all gaps and corners will reveal which is the problem. Post more photos if you like.