Feeders don’t come with a “birds will definitely find this” guarantee – “your money refunded if nothing nibbles within a month!” – but the birds will find them, eventually! One thing I have noticed is that, if for some reason I move a feeder even a few feet, the birds flutter around the space where it had been, and may not find it again for several days. This seems to imply that they are a bit slow-witted, but I am loathed to accuse them of that. More likely they have an initial wariness of a new position and are drawn to a familiar one that they associate with food.
My advice: give it time. Patience is a virtue.