sick chicken advice please?

4 or 5 is quite a good age for a hen, and if she is a hybrid it's really quite old. As she hasn't laid for a year, she's obviously getting on a bit. It's not very likely that a vet could do much to make her better, and your best course of action might be to just make her as comfortable as you can inthe time she has left. If she's still eating, that's a good sign that she hasn't given up yet. Try her with high-protein mashes made from soaked pellets mixed with chopped hardboiuled egg, or add sardines or hulled sunflower seeds. she may just die peacefully, but if and when you think she's in pain, the vet can put her to sleep quietly for you.

(Edit) Yes a gingernut ranger is a type of hybrid chicken, ie one that's bred to lay lots of eggs in the first 2-3 years, but sadly, after this time they tend to have less life expectancy than purebreed chickens because they're basically worn out sooner by all the egglaying. Hybrids have been developed for commercial egg production, where the birds are all culled before they get to two years old when their egg production begins to decline. They are not bred to live very long as this is unimportant commercially. So the lucky ones that end up as pets with kind people like you are doing quite well to make it to 4 or 5 years without too many problems.

Not sure what is wrong, occasionally get crouching when a hen is egg bound so you could check the egg duct. Most of my hens lived between 5 and 9 years. The only sign they were dying was usually losing weight. Vets will see them and they may know more. Good luck

I would advic you take her to the vet most small animal vet treat chickens . They are becoming alot more common as pets so vets are seeing them more. 5 years old isn't that old but you haven't said what breed she is as some breeds can live longer than other. It could be the vet could help she could have several things including infection. Chickens deserve vet care just like any animal when ill. They feel pain and suffer.