When using the store locator module for the first time your browser may prompt you to allow/deny location services.  Make sure you click "allow" to allow google maps to access your location.  Google maps requests to access location services and the browser must allow it or the location service wont be allowed. This is a privacy/security setting in your browser so make sure its enabled and you dont have your browser configured to "Deny location".  This will ensure that the Store Locator module can access your location and display the map properly.

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At your service,
Dave Smith