The battery is designed to fit securely in place and some pressure may be needed when inserting and removing it. Try to apply pressure around each lock at a time. You will know that each lock is fully secured when you hear a click sound - it should not be loose in any way.
If you suspect that the battery is not locked correctly, DO NOT take the board into the water. Instead, submit your details into our support form and someone from our team will be in touch to assist you.