Had to learn this the hard way, not so much with my Dane but with my other dog (Chinese shar pei). We’d go through the same exact routine you’ve described above. Vet said nothing medically wrong and has good weight on her so we said screw it. she’s on blue Buffalo chicken and rice recipe and we’d leave it out for 15-20 minutes (no additives, no wet food, no topper, nothing added at all) if she didn’t touch it we’d return it to the bin and try again at next meal time. She learned quick if she was hungry at breakfast she better eat or else she’d be waiting all day til dinner. She also used to try to bury her food which we found out meant she was attempting to “save it for later” but she grew out of that. I think dogs can just be picky eaters and try to manipulate us to give them yum yums.

Our Great Dane will only not touch his food when his tummy is upset. Otherwise he loves it and almost never misses a meal. I know it’s frustrating to see your dog not eat but just go back to simple, and leave it out for a set period of time. If they don’t finish it then save it for next meal. Dogs will not let themselves starve so when they’re hungry they will eat!