Well first off how old is she? If she?s much older than five and has never had a litter before then I would strongly urge you not to mate her now. A bitch?s hip bones begin to fuse fully after about three years of age so the ideal time is for her to have puppies is about 2 (it?s all give or take depending on the breed but a beagle is fairly typical) After five an unmated bitch?s pelvis is not always ?stretchy? enough for her to have puppies and mating her can cause a lot of unnecessary health issues.
Secondly, as others have asked, why can?t she have puppies? Like humans not all dogs are fertile and although it?s fairly rare she may simply be unable to conceive.
Provided that she is physically capable of reproducing then there?s no reason why a human fertility spell wouldn?t work although first you?d have to know, as said by Missjerseyb1, is to wait for her to come into season. Even with such a spell however it?s important to know the more ?mundane? methods to maximise your chances. The first signs is swelling of the vulva although this isn?t normally noticed by the owner so keep an eye out for vaginal bleeding. Once you notice small drops of blood on your floor/furniture she?s just about ready although a vet can help you determine the best time for the pairing to occur, although it?s typically about twelve days after the start of the bleeding.
If you do decide to get her mated then make sure you know what to expect during the event. With dog?s it?s not quite the same as people and the whole ordeal can be quite uncomfortable for the bitch. She will yowl, whine and make a general fuss, expect that so that you?re not distressed by it during the event. Also make sure you know what to expect during and after the pregnancy. Puppies are not a small matter and breeding is not for everyone, just make sure you do all the reading you need to and know exactly what you have to do. If you need help over it I?m happy to give advice, the first obstacle may appear to be the mating but don?t start it unless you?re ready for the responsibility. Puppies WILL require 24/7 care and it?s not all cuddles and sunshine, it sounds harsh but be prepared for the possibility that not all puppies will necessarily survive.