Agility - Golden retriever, Answer quick please!

Question
Hi, my Golden is good at agility... when she jumps. You see she is GREAT at jumping but sometimes she refuses to jump after about two jumps. All she does right now is jumping because I don't have the equipment for the other stuff yet. Anyway she doesn't jump because I think she's tired. But even when she isn't after about 2 jumps. Any tips to help her jump? Why isn't she jumping? Is she actually tired? Or is she just stubborn and not wanting to jump? Any agility tips?
Thanks
Sorry for all the questions!

Answer
Thanks for the question. I have a few questions that will help me answer your questions better. How high are you jumping her in practice? What conditioning routine(s) are you using in addition to jumping? How old is your dog? What surface are you jumping on? Thanks!