There could be many reasons why a cat meows at night, and the solutions vary. The cat might be meowing because it's hungry or thirsty; make sure it has enough food and water before bedtime.
Cats may have been sleeping with their owners for a long time and are used to sleeping in the bedroom. If you don't let your cat into the bedroom, it will feel uneasy and insecure. Bedrooms are relatively warm, and cats are animals that are afraid of the cold, so they will choose to sleep in warm places.
If it really affects the owner's sleep and life, you can consider using medication at a veterinary hospital or seeking help from a professional pet behavior trainer.
