Male dog not mating with female dog in heat

Question
I have 2 Shih Tzus, 1 male (age 11 months) and a female (age 5 years).  My female is in heat and keeps attempting to mate with male who seems completely uninterested in mating.  A month ago(before she went into heat)he seemed very interested in mating.  Now that she is ready, he has no interest.  I would like to have a litter of puppies.  Whats wrong?  Is there anything I can do?????

Answer
Hi Jay!
I would definitely recommend a vet visit.  A male dog does not reach full sexual maturity until up to 1 year of age.  His problem simply could be that he is just too young. Every dog is different.  Some males reach full sexual maturity by 6 months of age.
At age 5, I would definitely recommend blood work for your female shih tzu.  Make sure that everything is okay for her to carry a litter of puppies.  
Both dogs should get a wellness checkup before mating.  This will not only ensure the health of your female dog during the pregnancy and delivery of the pups, but also the pups health.  A pregnant dog needs veterinary check ups just like a human does.
There are millions of things to know before breeding any animal.  A vet visit would help tremendously with informing you of everything there is to know about being a repsonsible and reputable breeder.
After you have acheived what you wanted, getting your dogs "fixed" would be most beneficial.  Neutering a male dog eliminates the chances of testicular cancers, and decreases the chances of penile and prostate cancers by 98%.  Getting your female spayed will decrease her chances of mammary cancers by 99% and will eliminate the possibility of her developing uteran cancer and a severe and often times deadly uteran infection called a Pyometra.
I hope this has helped.  Best of luck with your vet visit,
Hilary