Plex iOS on iPad doesn't show all media! Plex iOS iPhone does. Why?

Firstly, I am using the newest Plex version for Synology and iOS.

If I add a new movie or mp4 file to my Synology NAS I can see it in the Plex App on iPhone, ATV or even via web browser but Plex on the iPad Pro 12.9 (2017) doesn’t show the new file. I don’t know how to refresh it. I re-installed the app on the iPad but no, I cannot see the new file. Why?