Plex app on Qnap will not open

Plex Media Server NAS & Devices
1

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

2

Go to www.plex.tv, log in and click on launcher

3

THANKS - I have done this but I see a message bar:
Plex media server update is available for server nap 1.10.1.4620 , download now

I download but has extension qpkg and will not open?

What now?

4

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