I, too, have heard nothing but good things about 'Nature's Miracle".
It could very well be that the dog has urinated in other locations which you are unaware of, and so cleaning that same spot repeatedly isn't going to help. You should be aware that the urine of all mammals will fluoresce under ultra violet light, and that any of the places listed under Janitorial Equipment in your yellow pages will sell ultraviolet lights made specifically for locating pet urine, or you can probably purchase them for less online. The amount of fluorescence will also give you an indication of how effectively your cleaner is removing the pet urine.
Here's a web site that caters specifically to the janitorial service sector of the economy, and if you use the Search tool on this site, you should find plenty of articles on the use of a black light to locate and remove pet stains. They call it a "Black Light" in the business, so search for the term "Black Light".
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