Asleep Map won't start after clicking start button

Once I start the Asleep map, it won't let me start the game after I click the start button. Affects Minecraft 1.12.2 but the map needs to be played on 1.8 but it shouldn't matter.

http://www.mediafire.com/file/27u58danxlqn4un/Asleep.zip

http://www.minecraftmaps.com/adventure-maps/asleep