When you have a balance available under “locked funds,” it means that there is an active bonus to which the balance is locked.
When the funds are locked, it is not possible to request a withdrawal until the wagering requirement for the respective bonus has been met. Sometimes the money is also locked to a specific product, and then you need to play on that product in accordance with the bonus terms and conditions. The specific requirements are always found in the Terms & Conditions for the promotion or in the notification you have received on the website/by email