The ground of every map is stored in a terrain file. Whenever you connect to a server that is running a map with terrain you don't have you download the terrain file for that map. If multiple versions of a single map exist or if somebody created a custom mod of a map for their own server then the terrain may be different between the versions. If your terrain map and the hosts do not match you cannot join the server.
To fix it, open up your add-ons folder. Look for the folder of the map the server you couldn't join was running. I'm not familiar with this Earth map, but I'll guess that it's name will be something like map_earth. Go into this folder and delete the terrain file. The terrain file ends in the .ter extension and will typically be named the same thing as the map (for example, earth.ter).
Reconnect to the server you were trying to join. You will redownload a copy of the terrain and be able to connect fine.
