Males can work a female until the cows come home, and copulate with them repeatedly, but they do not have what it takes to get the the girls to ovulate, which is what will have to happen before she has some babies. I went through the same thing you are going through with one of our pairs this past season. I will try again this year with a different male and we will see what happens.
Any more specific details you can share, can help us all help you figure out what could be going on. Good luck!
Jesse
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"Continuing to cling to the patterns you know, inhibits your ability to discover what you don't know." - Eric Allenbaugh