Cannot connect to FOP2 from browser
When opening up your browser and going to http://your.server/fop2 you see the message "One moment please, connecting to server, attempt 1,2,3..." and counting.
After a long while it finally display the message "Service Unavailable".
What you have seen is the browser attempting a websocket/xmlsocket connection to the FOP2 server and failing. That connection is needed so the FOP2 page can retrieve and show status in real time. It is a connection between your browser and the FOP2 server, using a different connection route than the browser has with your web server, and totally unrelated to Asterisk or the Asterisk Manager connection.
That connection is done by default using TCP port number 4445. So, in order for a successful connection between your browser and your FOP2 server, that port must be open/redirected at any router or firewall that might lie between your desktop computer and the FOP2 server itself.
Besides that, in the server the port is opened by the FOP2 daemon process. It is also used by the old FOP1 daemon. So, you also need to check that the FOP2 service is running and binding to that port (and that you do not have the old FOP1 running instead).
This wizard will help you find out the possible connectivity issues: