Before you open a support ticket, please make sure of the following:
That you have actually submitted a withdrawal request. When one succeeds, you will see an entry in the Pending Withdrawals box.
If you do not, please check the top of the page for any error messages.
Check out if you have entered more coins than you have.
If you do NOT have 2fa enabled, an email confirmation is required. If you do not receive this, please check your spam folder. At any time you can cancel your withdrawal and resubmit it to have the email sent to you.
OOOBTC use Cold storage, so it may take some time to process the withdrawal request, so you may need wait for a few minutes.