Background on IOS problem

hello guys, I’m really going crazy with a problem that I can’t solve in any way! my NC mobile app on ios is not working as it should, once the app is closed it does not continue its work and stops synchronizing the files with the server.
NC is on a server with ESXI virtual machine on freenas. I hope someone can give me some advice to fix this

Mine stopped uploading new media even when the app is open following the latest release.