Nyger Seed

Advice please?! We have been very successful with mixed seed and fat balls in our small suburban garden in Hampshire, attracting sparrows, blue tits, great tits, coal tits, plus other birds who hoover up underneath, like the robin, dunnocks, wood pigeons and collared doves. A very occasional greenfinch. But when we put out nyger seed in early July, in a brand new feeder, we had no customers at all for a month! We have gone back to mixed seed. Any ideas, whether or when we should try the nyger seed again? Thanks.