basic install of shiny server failing | CentOS 7

Greetings --

I had successfully been running shiny server on one of my CentOS boxes, but for some reason, it simply/completely stopped working. My usual approach is to simply do a full re-install. So, thats what I did (all as root).

1\ grabbed latest shiny-server rpm

2\ sudo yum installed it

3\ re-implemented basic firewall rules, just in case...

   sudo firewall-cmd --permanent --zone=public --add-port=3838/tcp
   sudo firewall-cmd --permanent --add-port=3838/udp
   sudo firewall-cmd --reload

No errrors.

4\ started shiny-server the usual way for a RTHEL/CentOS system:

systemctl enable shiny-server
systemctl start shiny-server
systemctl status shiny-server

Got the following:

Shiny-server.service - ShinyServer
Loaded: loaded (/etc/systemd/system/shiny-server.service; enabled; vendor preset: disabled)
Active: active (running) since Fri 2020-12-04 13:44:59 EST; 125ms ago
Main PID: 31975 (shiny-server)
CGroup: /system.slice/shiny-server.service
mq31975 /opt/shiny-server/ext/node/bin/shiny-server /opt/shiny-server/lib/main.js

Dec 04 13:44:59 systemd[1]: Started ShinyServer.

So, it looks as though all is well, although I have no idea what the CGroup line is telling me. shiny-server.log looks fine:

 2020-12-04T13:50:27.951] [INFO] shiny-server - Shiny Server v1.5.15.953 (Node.js v12.19.0)
 [2020-12-04T13:50:27.952] [INFO] shiny-server - Using config file "/etc/shiny-server/shiny-server.conf"
 [2020-12-04T13:50:27.982] [INFO] shiny-server - Starting listener on http://[::]:3838

5\ big moment -- test if all working. Simple http://localhost:3838

Fails miserably. Get a generic Page not found error. Nothing new in the log files. At all.

6\ if I try to point it at a previously functioning shiny app, I get

An error has occured. The application failed to start. The application exited during initialization.

When I look in the log, I now see the 'Error getting worker' message.

So, I'm completely stumped. Any suggestions as to obvious places to start working out the problem?

Hello cooch17,

Maybe it's a Firewall
Try this :

firewall-cmd --zone=public --permanent --add-port=3838/tcp
firewall-cmd --reload

As per my original post, I had already tried your suggestion.

This has me flummoxed. A basic, generic install, using the standard shiny-server.conf file, and...nada. localhost:3838 or both yield the same thing - page not found. But, all the samples files are there (in opt/shiny-server/samples/sample-apps).

Logs tell me squat -- merely that shiny-server is listening on 3838.