I’m so sorry to hear that you are having trouble with this little one.
Worst case scenario, if he/she continues to not eat (after the one meal that he/she did eat, that is), there’s an appetite stimulator that you can get from the HO’s Veternarian as a prescription and you simply rub a drop onto their ear and it works like a charm.
I used it when one of my cats had refused to eat for a short bit and within a very short time, his appetite had returned and he was right at his food bowl chowing down his meal.
Of course, you’d have to have the HO call their Vet, but certainly worth giving it a shot.
Best of luck. I hope it turns around quickly. Poor little angel baby! I hate when they are stressed like that. It’s just heart breaking.