No, cex.io is not a scam although it's facing withdrawal issue at the moment, it's not just you, there are a lot of customers complain about it.
You can try contacting
CEX account to verify your withdrawal.
This problem caused by their payment partner though
you can read this;
We understand your concerns and we kindly ask for an apology for the delays in payment processing. Nevertheless, it does not depends on us but rather on our payment partner. They are currently overloaded with requests and do not manage to process them properly.
As for now, the payments in USD and GBP are rejected and the funds are turned back to users' accounts. Furthermore, we would like to inform that wire USD and GBP transactions will be temporarily disabled on the platform.