If you have enabled Whitelist on your account, you can only withdraw funds from whitelisted addresses.
If your destination address is not whitelisted, there are three things you can do:
When you see this error, make sure that the destination address matches exactly the address added to your Whitelist. Also, check if Upper/lower case letters are matching.
Second, please keep in mind that you need to whitelist an address for each coin or token separately. So in case you have whitelisted some address for ETH withdrawals, you will not be able to withdraw a token to this address. You need to whitelist it for this specific token as well.
Most likely you have whitelisted the address, but additionally, to this address, you are using a Payment id (destination tag, message, etc.) when trying to initiate a withdrawal. The system won't let you do this. The payment id is an identifier of the destination where your coins will be sent. So you need to whitelist this payment id together with the address, using the special field.
Important: After adding a new address/payment id to your Whitelist, all withdrawals will be suspended on your account for 48 hours. You will see a notification about it on your Account page. This is a security measure for your funds' safety.