Maps Marker Pro needs a browser which supports Javascript in order to display maps. Current version of common browsers (Firefox, Chrome, Internet Explorer or Safari) support Javascript out of the box – if you use an old version, please update to the current version (you will benefit from it in general, believe me!).
If this doesnt help, please check if you have same Javascript blocking addons/plugins like NoScript installed and active – those addons need to be disabled in order to show maps.
If this does not help either, please open a support ticket and we will have a closer look why your map is not being displayed.