It is because they need to make sure everything works out by checking if this user is legit or not. Few months ago someone won alot here as well and they did check him as well , since the user was legit fortunejack then process her withdrawal. You can rest assure that fortunejack will pay in the end
Dear User,
Your recent winnings on Live Roulette has raised some doubts in the Fraud Protection department, we believe you understand the reason, so withdrawal will be altered until we confirm the authenticity of your play. Processes like this usually take up to 10 business days so accept apologies for the delay.