Did you changed your tortoise's diet recently, or is the food stale?
Did your tortoise just recently got out of its hibernation phase?
Is your tortoise kept in a colder place than it is recommended?
Does your tortoise shows any other symptom that may point to an illness (runny nose, swollen eyes, discolorations of the skin, etc)?
Your tortoise may not like their food. This is likely to occur if you have changed the type of food recently, or if it is stale and unappetizing to them. Try giving your tortoise something different, or one of their favorite treats, to see if this will get them eating again.
Tortoises tend not to be too hungry when they emerge from hibernation. They prioritize water and hydration over food and sustenance. While you do want your tortoise to eat as soon as possible after a hibernation, don’t be surprised if they don’t show interest in food for two or three days. Ensure that your tortoise has access to plenty of water when they first wake from his hibernation. Once they are fully hydrated, they should show interest in food again.
Tortoises are sensitive to temperature and need to be kept warm. If your tortoise is too cold, they will not eat as their entire system slows down. Ensuring that you have your tortoise away from windows, and other areas where he could catch a draft, is vital. Just as important is to ensure that you have a warming lamp in their living area.
There are several illnesses in tortoises that could cause them to not want to eat. The top three illnesses that generally cause a tortoise to stop eating are stomatitis (a mouth infection), respiratory infection, and intestinal parasites. If you suspect that your tortoise's loss of appetite is due to a health condition, you should take your pet to the exotics veterinarian for a check-up.
Digestion works slower in tortoises than it does in humans. If a tortoise gets backed up a bit, they will go on a self-starvation until things get moving and they have room for more food. Some experts suggest feeding your tortoise five days a week and withholding for two days.
https://peteducate.com/why-is-my-tortoise-not-eating/

Sreten null
Hi! I’m Sreten Filipović. I graduated from the Faculty of Agriculture at the University of Belgrade, with a master's degree in Environmental Protection in Agricultural Systems. I’ve worked as a researcher at Finland's Natural Resources Institute (LUKE) on a project aimed at adapting south-western Finland to drought episodes. I founded a consulting agency in the field of environment and agriculture to help farmers who want to implement the principles of sustainability on their farms. I’m also a founding member of the nonprofit organization Ecogenesis from Belgrade whose main goal is non-formal education on the environment and ecology. In my spare time, I like to write blog posts about sustainability, the environment, animal farming, horticulture, and plant protection. I’ve also published several science-fiction short stories.
You can find me on LinkedIn at https://www.linkedin.com/in/sreten-filipovi%C4%87-515aa5158/