How to challenge a loss

How do you challenge a loss? My opponent abandoned the game but it shows I resigned. How does that happen and do I challenge that?

You very probably got disconnected.    I don't know what type of connection you use but almost every type of connection can get disconnected-- even if you can still stream a movie.   Streams can build caches.  Chess games can't.

I don't think you can challenge it. (You can write to support@chess.com to see what they say but how can you prove you did not get disconnected?)

According to your archive, you have lost by abandonment 21 times, which is upsetting, until you check and see that you have won by abandonment 125 times...

I have had similar thing happen to me.. I think the only way is to rematch that is if the person is willing to play with you again

Is it possible to challenge a loss? I played my last move which was a checkmate, it played the checkmate sound, then immediately said i lost due to time. I played my last move with yeah very little time left, but i made the move on time. Showed checkmate, but still lost? Is there any way to challenge this?

No. Your move isn't official until it is received by the server. The fact that your device indicated that it was a checkmate is not sufficient.