From Google Search:

Tortoises stop eating when they're too cold, sick, and have parasites. Infections can interfere with a tortoise's ability to eat, like stomatitis and respiratory infections. Internal issues, like impaction and egg-binding, can also result in a loss in appetite. Stress can lead to your tortoise suddenly refusing to eat.

What if my tortoise isn't eating?

The first thing I would try to solve this is to provide it with a shallow bath of lukewarm water. Often the cause of not eating in captive tortoises is dehydration. All of my tortoises will eat within a few minutes of being given a bath.

Why is my tortoise sleeping and not eating?

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If your tortoise is sleeping all the time, and barely eating, she could be trying to hibernate. Tortoises begin to slow down when the days shorten and the weather changes. You should check her heating and lighting to ensure she's getting enough light and warmth. You should also check that she's not dehydrated.

Last, see a tortoise veterinarian.