I am so sorry you are having eating issues with your pup!
My little Tess, has a less than stellar appetite. She does have some kidney issues, her blood work indicates early kidney failure, but she continues to be relatively healthy on her kidney diet. Her kidney values have been off for quite a few years.
eeeefarms suggestion is a good one. Once Tess' appetite is stimulated, she eats well. Tess definitely plays food games, now that she is the last dog standing. She would often leave her food uneaten all day. These days, she waits for me to eat, and does want some of my food. I will usually give her a bite, or put a little on her her food. She does then finally, grudgingly finish her food.
I have hand fed her some days. That helps too.
Tess definitely has had tummy issues along the way. I will include famotadine (veterinarian recommended) in her pill pocket if her tummy is off. It does tend to help.
She has a bad neck, the result of jumping up and hitting the tailgate if my Volvo station wagon as it was opening. Poor girl, it bothers her off and on. During her last bad patch, she was on prednisone to reduce the swelling. It did work, but she lost her muscle mass and her appetite. I really thought I was going to lose her. She was so thin and weak. I think it's been over six months: she has recovered and is beginning to eat more normally.
Tess looks pretty good for a dog who is about to turn 16. I am grateful for every day I have with her.