Just out of curiosity how do you feed him? Do you still try force feeding or drop in some feeders and let him go for it? Sometimes my little guy will seem disinterested when I drop in food but will eat once I go away and stop staring at him. Also, I have some of that Zoo Med Pacman frog food which he won't eat when I wave in front of his face with tongs, but when I put it on the ground and wiggle it around he lunges at it like a spider monkey.

So perhaps it's a behavioral thing and your frog just prefers a certain way of eating? I'm no expert and only have a few months of experience but it's something you could consider if you haven't already.