Did you check if your Branch enabled Mendix Studio under [Version Control] → [ Manage Branch Lines] ?
In order to get all changes from Studio into Studio Pro you have to use the Update option in Studio Pro.
(And Commit to make sure all changes made in Studio Pro are synced with Studio again.
More information: https://docs.mendix.com/refguide/collaborative-development#4-1-merging-latest-changes
Thank you.
I did it with “Download from Version Control Server”. And everything is now up to date.