In order to use the web app, you need a browser that supports Web-GL. To check whether your browser supports Web-GL, please use this link. After you click the link, you should see a cube - if you a see green spinning cube, then your browser supports Web-GL.
If your browser supports Web-GL, but Inspect on the web still doesn't work for you, it must have been disabled somehow.
The most common reason of disabled Web-GL is disabled hardware acceleration in your browser. To enable it, please follow this guide (for Chrome v. 69 and higher, Firefox v. 63 and higher, or Safari v. 11 and higher).
NOTE: To check if Web-GL is enabled in Chrome open this address chrome://gpu/ in Chrome and search for WebGL