Check this: https://www.reddit.com/r/kucoin/comments/7qxy3w/for_everyone_facing_eth_withdrawal_issues/

Quote from the reddit post:
"If your withdrawal shows 'Succeeded' and your tx doesn't show in etherscan, most likely it has failed before reaching the network. Kucoin has to resend it manually, this will usually be done within 48 hours (usually around 30+ in my experience)."


KuCoin is aware of this so what you should do now: https://news.kucoin.com/en/eth-deposit-and-withdrawals-issue-provide-this-information-and-help-us-clear-the-transactions/