Hey @Aedu ,
I faced with the similar issue until I figure out the sequence of steps for configuration. After I configure co-authoring step be step in the following sequence - everything was perfect.
1) Turn on experimental feature
2) Press "connect" in Power Apps tab
3) Configure a repo in Azure DevOps
4) Fill in connection tab in Power Apps
5) Save and Publish the app
6) Close the app, refresh Power Apps portal (this was a key step without which I faced the issue)
7) share the app with co-owner
8 )open the app, edit, save, sync changes.
Hope this will help! 🙂