ResourcePack

It should work automatically, but if not, try the following:

1. Edit -> Resource Pack: Enabled

   

   Press Edit

   

   Resource Pack: Enabled
2. If you still have problems delete the server from your servers list, add it again and then accept resource packs.

   

   Press Proceed or Yes
3. If you still have problems - disable your own ResourcePack, it might conflict!!!

4. If you still have problems leave the server, go to %appdata%/.minecraft/server-resource-packs and delete everything. Then join the server again.

5. Nothing work? close minecraft and go %appdata%/.minecraft and delete everything, download new minecraft and try join!