My Banton Cochin Laying non-fertile eggs

[almadinapk]

I have a pair of black Bantom Cochin almost a year old. Both rooster and hen looks healthy and gel togather well, my hen has been laying since 4-5 months she lays only twice or thrice a week.
The Problem is that none of her eggs has ever hatched, I have tried both the ways by incubating and also by putting her eggs under broody. When I candel eggs on 7th or 8th day apart from that black bantom all other eggs shows progress. Can anybody suggest a reason for non-fertile eggs ??

 

[Mahonri]

do you need to trim feathers around the vents of both roo and hen.

Cochins are VERY fluffy butts and many breeders do the feather trimming thing.

If the other hens are getting fertile eggs from the same roo, then he's just not able to get the job done on her.