Verification plays an important role, as CEX.IO follows strict KYC/AML policies in its goal to promote bitcoin as legal tender. If your verification is rejected you should have received an explanatory email from our compliance department stating reason/reasons for its rejection. In case you do not agree with the comments or need any help - please review these guides that outline document requirements:
Of course, if you require any further assistance you can always contact our support team via support@cex.io - they will guide you through the process.