@tanza:
If a dog is otherwise health, they will eat when hungry…
Yeah Pat, I said the same things nearly my entire life. I quoted the "picky dogs are made not born" with all the info on finding a healthy diet and let them go without. Til I had sayblee who truly didn't care about eating and got to the point of being nearly skeletal. We ran every test on earth. I ended up force feeding her 2x a day for months– fortunately if I put it in her mouth and held it shut, she would swallow-- then was told to give cyproheptadine a try. It was a miracle. After dealing with her issues for almost 4 yrs, and her getting so thin her hipbones and back stood out (and like the OP, I tried every additive, raw, homemade lean meats.. nope, she ate enough not to DIE.
With a health issue, you might ask your vet about cyproheptadine. It is an antihistamine they found increases appetite in most mammals (including humans). It absolutely made my life and her's better.