After inserting the battery in the dedicated space, you will hear a sound signal. That indicates that your battery is correctly plugged. You can now screw the battery cover back on. After making 4 turns, make sure there is no gap between the battery cover and the battery compartment.
It is also recommand to check the good positioning of the joint present on the battery cover, which allows the waterproofness.
Also check that the joint is properly greased and that there is no impurities that could alter the waterproofness.