Favorites auto update

hello, on a set of ipad pro in iOS 11.3.1 I installed the application Nextcloud to allow access to our collaborators to different files of the company.

Of course it is necessary that these files are accessible offline (no Internet connection) so I added a folder in Favorites so that when I add a file or folder in this folder then it is automatically synchronized with the files. ipads. But despite several attempts synchronization is not done automatically. I am forced to launch the Nextcloud app and click on the folder to update. I realized the same on a file but the result is identical despite waiting more than 30 minutes.

In the options of the app I have activated “Offline Available Favorites”. My server is on nextcloud 13.0.4 and the app in version

Is there anything else to activate?
Thank you in advance.