They won’t eat it if they don’t recognise it as a food source and the same goes if they just don’t like it. If it is fairly new then just keep offering a small amount each day.
New foods can take quite a while to be accepted.
For foods my birds have consistently refused (like after months of daily offering) I just feed the left overs to the wild birds.
Birds are wasteful- no way around it so you just have to accept that we sometimes buy foods for them that goes to waste. I use the waste for either wild birds or my worm farm/compost then I don’t feel it’s wasted so much.