We have added the "Everyone" to our Observer Group in a Teams SharePoint site so that all employees can see some content; however, it keeps disappearing from the Observer group. We have added it back in 3 times and have checked the logs and cannot see that anyone has removed it. The 2 owners have not removed it.
Hi Becky. I recently resolved this "issue" at work. It has to do with the fact that there are two different security permissions (one for O365 Groups and the related SPO Teamsite that are mutually exclusive). If your O365 Group associated with your SPO Teamsite is set to private it will automatically (via a built in service account) remove the Everyone claim that you add to your SPO Teamsite in the Members and Visitors group. To work around this Microsoft default security measure create a new SPO membership group and add the Everyone claim in this newly created group. This will fix the "issue".