I believe that's an issue with your web browser... you can check if it supports WebGL2 here:
https://get.webgl.org/webgl2/
If it doesn't, you can activate it with these instructions:
https://get.webgl.org/webgl2/enable.html
Also, I believe the HTML5 version only works in Firefox Quantum: pease consider downloading one of the standalone versions in case it does not work!