?? I cant see any issue on your site.
1) What is your plugin environment? Please provide a screenshot of your plugin environment
2) Are you referring to being able to add a location under SLP Locations in the back end add? Do you have some other plugin like Smush that maybe clashing with SLP? Smush or any minify plugin can be turned off. SLp already mifies and there is a conflict with that plugin.
You can try debugging on the back end. There is an Enable debug under SLP /General tab, you can enable that and then try to perform the action and see if you get back any errors. and provide the error log or ffor better results ollow the WPDEBUG instructions in the troubleshooting docs