QNAP ts-453a PLEX APP can't connect to server

I am new user of QNAP TS-453A, and attempting to add PLEX app. I have searched the PLEX forum for answers related to problems of mine, and have not found any topics. Here is my problem:

On the QNAP GUI, I downloaded the PLEX app, but when clicking the icon to open the app, I get this error:

"Safari Can’t Connect to the Server

Safari can’t open the page “72.234.32.163:32400/web” because Safari can’t connect to the server “72.234.32.163”."

I have removed the app from QNAP, re-installed it, but get the same error.

Any ideas on how to run the app on my QNAP NAS?

https://forums.plex.tv/discussion/175405/qnap-faq-read-me-first#Q22