When trying to open a dwg file an error message is displayed, stating "[file_path\.dwg] is not in a recognized file format"
When you open a higher version of dwg file in a lower version MS RealDWG, this message is displayed. MXRoad SS2 supports RealDWG 2009 or 2010 so that you can open 2010/2011/2012 dwg version files but not 2013/2014. MXRoad SS3 supports RealDWG 2013 or 2014.
You can download the latest version of RealDWG, which is version 2016, here: https://softwaredownloads.bentley.com/en/ProductDetails/2150