It is possible that you accidentally copied a Bitcoin address instead of BCH. Coinbase uses p2sh Segwit addresses for Bitcoin and the address you sent to is also p2sh. When converted to legacy format the address is 3L8yHKLYoFJYSjj6XVwYpDJ5upHV8giwnp. You might want to check if that matches one of your BTC addresses on Coinbase.