breading problems

Question
My dog is in heat and she allows my sire to mount her. The problem is he can"t penetrate her. what can I do to help him. Do I have to get her invetro fertilization. Please help.

Answer
Hello

What exactly is the problem?  Is he too short?  Does she dance away?  What day in her season is she?  Are they both inexperienced? Does he not come out all the way?  Is she too tight? What breed is she?

If you could give me more information to go by, I can better answer your question or at least help you figure out what needs to be done.