Not 100% sure but the community's Video FAQ contains this post here:
Feb 03,2015 Question: How to capture a screenshot of the current menu screen on the HDX , QDX or GroupSeries systems?
Answer: Open a web browser and navigate to http://systemIP/currentscreen.cgi
Jul 22,2014 Question: How can I enable the “Allow Video Display on Web” option on a HDX?
Answer: This must be enable via the HDX GUI first via the remote => System => Admin Settings => General Settings => Security>Security Settings page 3 (Depending on the Software Version)
NOTE: You must use the systems remote control to do this !
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's