If you are being randomly kicked from the classroom to the lobby screen, then please check that you are using the latest version of Chrome. Older versions of Chrome may not support features that Engageli relies upon and when those features are utilized in the classroom, it may cause in users with outdated browsers to be redirected to the class lobby.
To see the latest version of Chrome, you can visit Google's Chrome Releases page: https://chromereleases.googleblog.com/search/label/Desktop%20Update
Users on ChromeOS may sometimes find that they are unable to update their Chrome to the latest version. This is likely because their Chromebook has reached its Auto Update Expiration (AUE) date and can no longer be updated. At the time of this writing, the typical AUE on Chromebooks is 8 years from the date the device was released. This is a Chromebook limitation and the easiest workaround is to use a different device.