I find that my L066 (Go to planetcatfish.com to see him. It was the site that helped me figure out what type of pleco I have.) I nearly have to toss the food in his cave in order to make sure s/he eats. Also, if anything changes, s/he will stop eating for a day or two. S/he is a beautiful pelco, and starting to settle in nicely now. Also, try different sinking food. I mean, L066 loves sinking tablets and will pull them into the cave. HOWEVER s/he wants nothing to do with Algae tablets.
I have 6 common pelcos in my 75-gallon tank. I have a bit of challenge making sure everyone is eating, but as long as no one looks skinny, I am thinking they are fine. (The man moved in and his fishes came with him, and the fishes moved into my 75-gallon tank, which was under stocked anyway.)
Now what were his three LOVE algae tablets, to the point of everyone gets their own chip, but will not touch the sinking tablet that L066 loves. What were my three eat anything that sinks to the bottom on the tank and does not move. I make it a point to see that at least 8-10 algae chips are in this tank, as well as 3-6 sinking tablets when I feed them. (It also has Ottos and a catfish in it, so all that food does go!)
So try different things and see what you can learn from the web about your golden nugget. I mean, it was after I discovered L066 was not eating the algae tablets, did I learn they are more of meat-eaters! So of course he will not eat the Algae tablets, (and I make it a point to see that he has at least two to eat, so my platys don't look like a snack!)