Azoospermia is the medical term for a zero sperm count. This means that a man has no sperm in his ejaculate at all, something that obvious represents a fertility problem! The specific diagnosis of azoospermia can only be made following a sperm analysis; couples who are not pregnant after a long time of trying to conceive may know there is a problem, but they wouldn't know where until they went for medical testing.
Once you go for fertility testing, and azoospermia is discovered, finding the cause of the zero sperm count is prudent. There are several causes, which can be divided into two major groups: a sperm production problem or a sperm delivery problem. The first means that a man doesn't make any sperm, and the second means that he does create sperm, but for some reason it doesn't end up in the ejaculate. Sperm delivery problems resulting in a zero sperm count can, for instance, be caused by a lack of the vas deferens the tubes that carry sperm from the testicles to the penis. Alternatively, those tubes may have become blocked (due to hernia, sometimes) or sperm may be exiting into the bladder instead. In the first case, it is obvious that homeopathic treatments cannot possibly make the body grow vas deferens. Where there is a hernia, it's also pretty obvious that homeopathy is not adequate to treat that... even to people who normally believe that homeopathy can work.
Now, let's take a look at sperm production problems that lead to a zero sperm count. This can be caused by the lack of essential hormones that are needed to make sperm, or in some cases a varicocele. This is a swollen, dilated vein in the testicle. Azoospermia, unlike a simply low sperm count (and then only in some men), can't be cured by simple lifestyle changes that boost overall health and fertility. There is more going on. We'll have to conclude by saying that homeopathy cannot cure azoospermia. If azoospermia can be cured at all, it will need serious medical intervention.