Mine do this, mostly at breakfast time, and I refuse to pander to them by keep changing it but I do add something tasty to get it down them. The other day it was 2 scrambled eggs between the 4 of them, sometimes it's a mashed up tinned sardine, sometimes a bit of grated cheddar. I only really do this because they are all quite slim and Indie is ancient and loses weight really quickly but sometimes I just get really hacked off with them and bin it. They usually eat their tea later
My terrier was the same, and once all health/medi conditions were ruled out it was good ol tripe that got him back onto dried, just gradually reduced the tripe ratio daily. Good luck - some will say he will eat if he is hungry.