Is there any configuration of Free Cell that cannot be solved?
It's not hard to prove that an unsolvable start exists. Just imagine a start where the only possible first moves would be moving cards to the extra cells. In some versions, -1 and -2 are examples of this though the only way to play them is to choose that seed.


If you only count setups which can exist in normal play, seed 11982 in the Windows version is an example of this:


Of the original 32000 games in Freecell, 11982 is the only one for which no legitimate solution was found. Since then, several computers and players have failed to find a solution- to the point where every possible combination of moves has been tried and has failed.