Well "experienced reefers" have told me lot's of things that they deemed impossible over the nearly 40 years I'm in this hobby and I proved them wrong more often than I can count.
I never tried twin spot gobies, but my impression is that they are, like the Valenciennea gobies, almost always infected with intestinal parasites. A proper "deworming" might be the first step to success.
Another reason for the often observed starvation problem may lie in the way they were caught. I would avoid specimen from Indonesia where they may be caught with cyanide and rather get them from places that are know to only use nets.
Another issue may be a too long starvation period while in the supply chain.
I somewhat doubt that they are actual food specialists. They chew through sand and likely sort by taste. So I would expect them to take anything edible they find in or even on the sand. Seeding the sand with a small frozen food like Cyclops might be a good start.
Sinking pellets that lay on the ground may work as well and would be a good way to give them some extra meals during the day.
Another thing to consider is that they live in pairs in the wild. Alone they may feel uncomfortable. I posted some links to some articles
here about pair formation and why fish may pair up. One finding was that one partner looks out for predators while the other feeds. So a lonely fish in a new environment may not eat because he is missing his "lookout".
