You activated the Store Locator Plus base plug-in and followed all the instructions but when you visit your locator page no map 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 Google 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. See Getting Started Guide. More recently, 2018, Google has introduced security measures requiring SSL certification (HTTPS) for sites that may want the search to locate their customers location. (Location Sensor)
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.