Co Authoring with Sensitivity Labels

Hello Tiffanyb​ ,

Do you have this issue with all the labels in the Highly Confidential label group?
The label "All Employees" sould have the autosave on since the default  permission setting allow all internal users to edit and save encrypted documents. 
I'd confirm that affected users / groups have proper permissions configured for co-authoring. 
Also note that in certains scenarios the feature will not be available. For example, co-authoring and AutoSave don't work for a labeled and encrypted document if another user has it open in a Office desktop app that doesn't support the new labeling metadata. 

https://learn.microsoft.com/en-us/purview/sensitivity-labels-coauthoring#limitations 

https://support.microsoft.com/en-US/SharePoint/get-started-with-sharepoint/document-collaboration-and-co-authoring