There are two problems with your FEN string:
1 - In your FEN, the ranks are listed in reverse order. They should be listed from rank eight to rank one.
2 - If it's black's turn to move, then the 'w' should be a 'b'.
I think this is what the FEN string should be:
[Site "Chess.com"] [Result "*"] [SetUp "1"] [FEN "r2kq2r/1pp3pp/3p1nb1/2n1p2P/pbP3P1/2N1BP2/PP3N2/K1R1QB1R b - - 0 1"]*
https://www.chess.com/analysis/game/pgn/3YPTqkEmQS?tab=analysis
[Site "Chess.com"] [Result "*"] [SetUp "1"] [FEN "K1R1QB1R/PP3N2/2N1BP2/pbP3P1/2n1p2P/3p1nb1/1pp3pp/r2kq2r w - - 0 1"]* I saw this mate online, but it was black to move. knight goes g6 to check king. but then it becomes a mate, and pawn is unable to take.