Running firefly on a slug wired to a Buffalo whr-hp-g54 that’s running dd-wrt v23 sp2. Works fine with both wired and wireless clients. i’d don’t *remember* changing any multicast options from stock but I’ll check that out for you. Have you any clients (wired) that can see the server?
Other possibilities for non-library discovery could be;
1. Active VPN client on the server.
2. Anti-virus with ‘worm protection’ on the server.
3. Anti-spyware on the server.