Be sure to read https://yatse.tv/wiki/debug-yatse-kodi-remote to provide necessary logs and information.
I have connected Yatse to my Plex server. In the Movies tabs, I can see files that are not part of my Plex Movies library. Instead, these files are part of other Plex libraries that are of type “Other Videos”.
Those “Other Videos” libraries btw are not shown in the left navigation bar in Yatse, would be nice if they could be shown as well.