When troubleshooting machine seeing machine on a network, PING is the basic place to start.
If one computer is 192.168.0.12 and another is 192.168.0.13, pinging the one IP address from the other will tell you the latency (time it takes) for one to ask and the other to answer. (you would expect the numbers to be low ~.034 msec)
If one is connected to a router with IP address 192.168.0.1 and the other connects to a wireless router with IP address 192.168.1.1, there can be a problem with the Mask (typically 255.255.255.0)
They are both on the same network... both off of a juniper router.
I am not at the computers right now, but I will check the IPs next time I am there.
You can have a Firewall on the router that is blocking the port needed by Filemaker.
You can have a Firewall on a computer that is blocking the port needed by Filemaker.
You can have TWO Firewalls on a computer that are both blocking the port needed by Filemaker.