Muscovy egg fertility ?

I have a friend who's been selling "fertile " eggs and now it seems that her drake is shooting blanks ? Is there a time in the whole breeding process where the hens go through a dry period ? She has never had this happen and I've borrowed her my Drake that I raised from one of her ducklings that came from her stock to see if it's her drake ? We have both tried to find some info online but it seems that we're not finding any usefull info in regards to this .Anyone out there have had this happen to them ??

I wouldnt say the hens go through a dry period but they would be picky on drakes. Has she seen the drake actually perform? Some hens will not let a drake breed them, other things I have read said they can actually expell the semen from a drake they did not wish to mate with? Could be an issue.
And I know muscovies do not require water to breed but I find my fertility increases a lot when they have a kiddie pool to swim and breed in.

There are two drakes that are with the hens and my drake is a offspring from one of them ? they had no problems last year ?? Right now my drake is in with them and I'm being told he's a real ladys man ?? so maybe they will accept a more passive partner ?? sounds like the other two males were a bit aggresive ? O guess we'll see in a few week/months if it helped