Auto upload does not work on Android 4.3

dear friends.

I have an issue with my samsung galaxy camera 2 (Android 4.3) and the nextcloud app (3.1.0).
the auto upload does not work. i know it is quite old but i have 3 pieces working in my company really well.
the automatic upload is turned on in the app and works if i force a rescan.

is there something that i have missed ?