en passant
Also it may help to do it immediately after the advance of the opposing pawn. *mumbles something about overly rigid, fascist rules*

See the symbols by some peoples names, gold, diamond, platinum, etc.
OTOH, Chess.com allows all of the legal moves to all levels of players, just to make sure the jokes don't confuse newcomers. Read the rules of chess for en-passant to make sure you know how to do it correctly.

when I try the move it doesn't execute the move. I'll try again then.
https://en.wikipedia.org/wiki/En_passant
please point us to the game & move you tried.
If chess.com didn't allow en passant, that means en passant was not a legal move at this moment.
Read the rules of chess for en-passant to make sure you know how to do it correctly.

@stdavid, can you be more specific. I don't know of a way to use the Chess.com computers to analyze a game in progress. Can you specify how you are able to do this. Hopefully if there is a bug in the code the chess.com people can fix it.

chess.com does not recognize this move. Has anyone heard of it?

#17 I thought it was 1982 that en passant was removed. The 1979 ruling was merely an amendment.