Installed the plugin for a peak and it looks great.
It looks like you are hard coding the plugin's file locations to /wp-content/ which means it won't work on any site that has moved or renamed that directory, which is not completely uncommon.
I found it on line 219 of storelocator.php.
If this makes things too complicated or breaks something else, no worries. A simple rewrite rule in htaccess solves it for me and will work for others who have non-standard installs.
It's good work you're contributing to the community and sincere thank you for it.