This often means your internet connection is not strong. Try to troubleshoot the issue by:
Make sure your computer, laptop or smart device is as close to your Wi-Fi router as possible. Try leaving the class and rejoining. Unplug your router and modem, wait 30 seconds, then plug it back in. It may take several minutes for your internet to reboot. This often solves many internet issues. Contact your internet service provider to help you troubleshoot.