In which case, the transaction is in Cex's queue and has not yet been broadcast. They may be waiting for a sufficient volume of withdrawals to batch together, or they may have other internal factors going on which is slowing down the process, such as the recent spike in transaction fees and backing up of the mempool. I would also check your email and make sure they haven't seen you a notification saying they require additional information, KYC, 2FA code or something else before they will process your withdrawal.

There is nothing anybody on this forum can do to help. The only people that can solve this is Cex. If their support is not answering your messages, try reaching out to them on social media: https://twitter.com/cex_io