Google API key
By default, the MapSearch 2.0, RouteViewer 3.0 and PoiViewer 2.0 plugins load the Google Maps API without a Google API key, but this API key is required (see here). Therefore, you should provide the plugins with your Google API key by setting the map.api.key parameter (find out how on the plugins' respective documentation pages, see the previous links).
If you don't have a Google API key yet, go to this page and follow step 1. Step 2 is not necessary, instead insert the API key into the plugin's configuration object.