According to the computer a blunder is made and I can't find it. It may be my opponent's blunder or mine.
You might give us a clue what game you were talking about, and whether you were using the web version or one of the apps.
But on the web version, the blunders are easy to find. They are marked in red.
According to the computer a blunder is made and I can't find it. It may be my opponent's blunder or mine.