Okay so i'm having this problem too, here are the logs
Server protocol version 2
[22:57:38] [Netty Client IO #7/INFO]: Attempting connection with missing mods [] at SERVER
[22:57:39] [Netty Client IO #7/INFO]: Injecting existing block and item data into this client instance
[22:57:39] [Netty Client IO #7/INFO]: Found a missing id from the world appliedenergistics2:tile.BlockSkyChest
[22:57:39] [Netty Client IO #7/INFO]: Found a missing id from the world appliedenergistics2:tile.BlockSkyCompass
[22:57:39] [Netty Client IO #7/INFO]: Found a missing id from the world appliedenergistics2:tile.BlockSkyCompass
[22:57:39] [Netty Client IO #7/INFO]: Found a missing id from the world appliedenergistics2:tile.BlockSkyChest
[22:57:39] [Netty Client IO #7/INFO]: Reset configs to client values for com.enderio.core.common.config.ConfigHandler
[22:57:39] [Netty Client IO #7/ERROR]: Failed to connect to server: there are 4 missing blocks and items
Im playing crundee craft and have my own server, ive checked and double checked to make sure all versions are the same.