Signage Manager communicates with media players through local area network (LAN). Please make sure below ports are opened & not blocked.
Hypertext Transfer Protocol (HTTP), main communication port with legacy players (e.g. NMP-302w, NMP580-W, EP1031, EP1032, EP1042T, CDM4300R, CDM4900R, CDM5500...).
HTTP alternate, main communication port with all players.
For cloud update service through Google drive.
Microsoft Simple Service Discovery Protocol (SSDP), to discover players on the network.