Plex app on Qnap will not open



I log onto my Qnap via web browser - click on installed Plex app and it will not open a browser page.

I have removed and reinstalled still no good


Go to, log in and click on launcher


THANKS - I have done this but I see a message bar:
Plex media server update is available for server nap , download now

I download but has extension qpkg and will not open?

What now?


.qpkg files are QNAP package files and must be installed on the QNAP through App Center