Good advice if the L264 was a carnivore, but it's not. Not really an omnivore either although they do like occasional meats like krill, which is a favorite.
More of an herbivore than anything. Mine eats more algae than anything else and loves diatoms. Loves cucumber, zucchini, potatoes with occasional wafers and pellets, and relishes krill.
Generally takes a week or so to settle in. Very nocturnal and likes to stay hidden during the day. As a general rule of thumb, I find most plecos seen making sorties during the day are usually not getting enough nutrition. Most happy loricariids will eat and be most active at night. Try feeding after the lights are out.
I installed lunar lights on both of my tanks because it's the only way I get to see them.
And yes, fish can go weeks without food. Watch for a sunken belly and sunken spots behind the eyes. Patience and a stress free environment are key. Good luck. Wonderful fish once settled.