Rescue dog doesn’t know how to play

I rescued a dog 4 months ago. She’s a big white dog, probably a mix of something, maybe Maremma or Great Pyrenees. She’s approximately 3 years old.

Ever since I got her, she’s been dealing with a lot of physical issues: allergies, surgeries, and more. It’s been stressful for both of us.

She is very anxious. At first, she didn’t even want to be outside, maybe only at night. Now she’s more comfortable, but she’s very scared of men, and I think she was abused by them.

At home, she mostly just lies there. She has three spots where she likes to be and switches between them sometimes. When I give her food, she never eats it right away usually only 4–5 hours later. So she’s not food-motivated.

I tried to play with her, but she doesn’t seem to understand what I want from her. When I use a ball, she flinches when I throw it. When I try something else, she just doesn’t care.

One time I covered a ball with cheese and she got excited and started licking it, but when it rolled too far away, she just stopped.

She doesn’t like a Kong and only tries to lick the inside, never uses her paws. She did like rope toys, when I put snacks in them, she tried to get them out, but after like a min she stopped.

She’s not scared of other dogs. Usually she wants to sniff them, but nothing more. When they try to play, she just walks away.

Now, because of food allergies, we can’t give her any snacks. So I can’t motivate her with anything except long walks.

What do I do? How do I bring joy and play into her life? Please help, I want her to be happy!)