Hi All,
We apologize for the inconvenience caused.
We understand you want to know why users received the notification when Microsoft 365 admin didn't make any changes.
Considering that different users from different tenants are experiencing the same issue, it seems more like a server side issue and need to be fixed from back end.
We have checked the current service incidents from our side but didn't find any related incident.
In this situation, we sincerely recommend you follow steps in this article Get support - Microsoft 365 admin | Microsoft Learn to raise a support ticket and report this issue to Microsoft support team.
The more reports they receive from different customers, the more likely they will be able to find something affects users in common, do investigation and fix it soon. They have higher permission and more resource than us. This would be the most efficient way in handling this case for you.
Thanks for your cooperation and understanding! We hope you are keeping safe and well!
Sincerely,
Tina | Microsoft Community Moderator