Conditional Move - En Passant

I was trying to make a conditional move (which I have done many times before), but have not come across this until now. I was trying to make an en passant conditional move but it listed it as an error. I know the rules to en passant: your pawn has to be on your 5th rank (which it was) and your opponent moves a pawn that is adjacent to your own from his 2nd rank to his 4th rank. You can then immediatley (cannot wait more than a move to do the en passant or it will be invalid) take your opponents adjacent pawn "en passant" by going behind his pawn diagonally one square (as if he moved his adjacent pawn only one square --- ie. like an ambush). The en passant move that I made was done correctly, but the site didn't recognize that is was legal to do so. Is there a glitch in the system? Can this be fixed? Thank you for your time.

You seem to be fully aware of the en passant rules, so yeah, probably a glitch/bug where the conditional-move mode doesnt know what en passant is.
I would send feedback, or you can wait till Russ reads this and hope he replys, notes it.