hmm can you install IE11 (if you haven’t already) and then make this registry change (browser emulation) Enabling HTML5 in the Windows .net Player
also please make sure you have fully qualified path to the CMS library in CMS settings - Library location section of this post Xibo CMS Post-Installation Setup Guide
If the problem will persist after above is done correctly, could you please show us a screenshot of status window on your player?