Why are my eggs unfertile

[Chicky 13]

I bought a proven rooster 3 weeks ago but all of my recent eggs are unfertilised. I know he has fathered chicks before but since arriving he has not mounted any of my 4 ladies. I attached a picture of an egg, it doesnt have the bulls eye so its definitely not fertile right? Any help appreciated x

 

[Kiki]

Give him some time.
They(him and the hens) are still "new" to each other.

 

[Chicky 13]

Give him some time.
They(him and the hens) are still "new" to each other.

Youre probably right.