The URL in the JSON pack is outdated or requires an authentication token.
Use the Full FBNeo JSON Pack for the true auto-download experience. fc2 json pack -auto download roms from fightcade 2-
Now, configure Fightcade to use the new pack: The URL in the JSON pack is outdated
If you are technically inclined, you can create your own JSON pack to auto-download ROMs from your private server or local network. fc2 json pack -auto download roms from fightcade 2-