This article explains what all to check when the PAA web UI does not show up.
The login page for PAA does not load after agreeing to the certificate for the browser.
You can check the following things to check if the service is up or not
Command to check the same is: ncc services status
If the service is down, try to restart it with the command: ncc services restart
You can use the netstat -antp command to check the same.
If none of these work, please contact JTAC.