There are numerous articles and documentation about setting up your Google API. I do not see that error when visiting your site so cant be sure if that is your issue. But also you should update to SLP version 5.0.5 ( See changelog here under development, that was fixed in version 5.04) That may fix the issue, there was an issue with Map regions /domains not saving and defaulting to the US, make sure you have selected Australia for your Map domain under the Settings/Map functionality
I went to your site and nothing as far as Google geocoding came back when searching that suburb.
BUT
What i do see is this error
Mixed ContentThe page at ‘https://www.sloggers.com.au/store-finder/‘ was loaded over HTTPS, but requested an insecure favicon ‘http://sloggers.wpengine.com/wp-content/uploads/2015/03/favicon.jpg‘. This request has been blocked; the content must be served over HTTPS.
And that can on cause the Google API to hiccup. See Mixed Content info