The lid locking tabs aren't fully engaged with the base handles.
- Place the lid on the stoneware, aligning it with the front and back of the oval.
- Push the lid down firmly until it seats evenly all around.
- Rotate the locking latches on each side downward until they click and lock under the base's handles.
If that didn't work, check that the silicone gasket on the underside of the lid is seated correctly and not pinched or folded. A misaligned gasket prevents a proper seal and lock.
Heads up: Never force the latches. If they don't rotate smoothly, the lid is misaligned. The lid must be locked for safe transport to prevent spills.