That's expected. Firefox unless not Tor browser should not show anything since the onion addresses are available inside the Tor network only. Think about it as hostnames on your local network, nobody else can access them only the clients already on the network.
Discussion
Yea, but running firefox over Tor doesnt work. My assumption is it can only access clearnet sites, for some reason, despite being in Tor. Maybe it needs a special extension like i2p sites?