You may have noticed that the version 57 of Google Chrome brought some changes with it. Long story short, if you are not a certain tab, Chrome may put it to sleep to use fewer resources, which in principle is a nice concept, but this may interfere with screen sharing interactive applications. In order to avoid delays, We recommend disabling "Throttle expensive background timers" for Presenter/Teacher.
Open a new tab in Chrome, and paste this into the address bar and hit enter :
Locate the line with “Throttle expensive background timers” and choose disabled from the drop-down options. Then, at the bottom of the screen, hit relaunch to restart your browser.