Firstly, it is not a ProStyler Theme issue. Google changed the way that Google Maps works. Since June 22, 2016 Google does not allow map requests without an API key. This fix should also work for other themes as well.
Here's An Easy Fix:
1. Make sure your using the latest version of Prostyler. The latest version is Version: 3.21. If you are using a version below 3.12 you will need to watch this video and apply the fixes I give. Once you do this all Theme Updates will show up in the WordPress dashboard.
2. Get a Google Maps API key here.
3. Install a plugin called "API KEY for Google Maps" WordPress Plugin. You can find it here.
If your interested in why Google decided to make the change, this article explains why.