I'm going out on limb here having been a newcomer to FOP2 but in most instances I would expect FOP2 to be on the same server as Asterisk, and the AMI.
However having said that if you have FOP2 running on another web server and you have ensured that it is configured to connect to another server hosting Asterisk and the AMI and the required connecting ports are open along with using the correct AMI authentication as defined in
/etc/asterisk/manager.conf
and
/usr/local/fop2/fop2.cfg
Then in theory this would also work, Some more experienced users please correct me if I am wrong.
Also when testing using /usr/local/fop2/fop2_server --test
Would confirm that FOP2 can talk to Asterisk AMI
I found this out by trial and error