I had the same problem but i got it to work with some adjustments. Open the config.xml of the instance and change the following:
1) change <property name="GameMode" value="GameModeSurvivalMP"/> into <property name="GameMode" value="GameModeSurvival"/>
2) change <property name="GameWorld" value="Random Gen"/> into <property name="GameWorld" value="RWG"/>
3) change <property name="ServerDisabledNetworkProtocols" value="SteamNetworking"/> into <property name="ServerDisabledNetworkProtocols" value=""/> (you need SteamNetworking at least if you have set a passwrod for your server
4) add line <property name="PartySharedKillRange" value="100"/>
5) add line <property name="ServerVisibility" value="2"/> (2 means public, 1 only shown to friends, 0 not listed)
6) add line <property name="WorldGenSeed" value="yourSeed"/>
After that the server started, created the map and i was able to join.
Dunno about the MapRendering thing.