[Date "01/02/2021 11:52AM"]
[FEN rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1]
[White "Beth (20)"]
[Black "Drew0Kelvin"]
[WhiteElo "2500"]
[BlackElo "1200"]
1.e4 c5 2.d4 b6 3.Nc3 d6 4.Nf3 Nf6 5.dxc5 bxc5 6.e5 dxe5 7.Qxd8+ Kxd8 8.Nxe5 Be6 9.Be3 Na6 10.O-O-O+
You moved your king in move 7. One of the castling rules is that the king and the rook you are castling with never have moved.
https://support.chess.com/article/266-how-do-i-castle
[Date "01/02/2021 11:52AM"]
[FEN rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1]
[White "Beth (20)"]
[Black "Drew0Kelvin"]
[WhiteElo "2500"]
[BlackElo "1200"]
1.e4 c5 2.d4 b6 3.Nc3 d6 4.Nf3 Nf6 5.dxc5 bxc5 6.e5 dxe5 7.Qxd8+ Kxd8 8.Nxe5 Be6 9.Be3 Na6 10.O-O-O+