i had this problem mate, a right pain in the ass and very embarrassing when u gotta climb over the passenger seat lol
it happened last winter for a day but i managed to loosen it by turning the key a few times and that was it
but this winter that didnt work, had to get someone to put a wire coat hanger down the window to open the door, once the door card was off it turned out to be the mechanism was jammed, the lubricant was dried out and it jammed. they dismantled it, cleaned out all the parts, greased them up put it back together and bobs ur uncle