You activated the Store Locator Plus base plug-in and followed all the instructions but when you visit your locator page nothing is there.
Here are some common reasons why the map will not appear:
Did you obtain a Google MAP API key?
As of June 22, 2016 Goggle requires all new domains, sites to obtain a key. There are many options based on how often your locations are queried. There are instructions in the SLP documentation site , in the SLP User Interface under INFO.
Here is a link to the Google developers console to get you started.
Check your web browser debug console. All modern web browser have it including Internet Explorer (IE), Chrome, Firefox, and Safari.