Quick answer: Unity Netcode for GameObjects NetworkObject spawned on server not appearing on clients? Prefab must be registered in the Network Prefabs list - missing registration silently fails.
Server calls NetworkManager.Spawn(prefab). Server side: visible. Client side: nothing happens.
Register the prefab
NetworkManager > Network Prefabs. Add the prefab. Without registration, clients can't deserialize the spawn message.
Verify the GlobalObjectIdHash
NetworkObject inspector shows a hash. Hash should match across server and client builds; differences = stale prefab references.
Check network logs
Enable NGO verbose logs. Could not find prefab messages on clients point at the registration gap.
“Network prefabs are typed by hash. Hash mismatch = silent failure.”
Build a CI check that compares server and client prefab hashes. Drift surfaces immediately; no more 'why won't this spawn' debugging sessions.