The cat keeps meowing because it's locked out:
Cats lack a sense of security. Although cats may seem fearless, they are actually quite timid. Cats prefer to be in the same room as their owners, and seeing their owners makes them feel a little safer.
Cats are very curious. If a cat is locked outside, it will be very curious about what its owner is doing inside.
The cat may not have adapted to its new environment yet. Especially kittens that are not yet adults need a lot of love from their owners to gradually adapt to their new surroundings. If you lock it outside, it will feel abandoned.
