I have had really good success getting picky angels like flagfins, potters, and singapores to eat NLS pellets even before they ate mysis. It's worth a shot.
In the meantime, as Matthew says, be sure that the tank (hoping it's in quarantine) has live rock that the fish can pick at for algae and pods or whatever else they look for when they pick at rock. My angels also go absolutely nuts for Sera spirulina tabs.
Live brine, while nutritionally poor, can often evoke an eating response that can be expanded to other frozen food, like mysis.