No I do not know why. Since you have restricted how many km the pull down menu radius is showing I cant “get there from here” when I do a search.
We do not calculate the distance, Store Locator Plus queries Google for locations. How the Search works
Excerpt : The way the base plug-in works is that it takes the selected state, asks Google what the geographic center of that state is, and uses the latitude/longitude Google returns as the starting search address.