I'm not connecting to my Friend's Realm

The game won't connect to my friends realm it says " Unable To Connect To World" It breaks at "Loading Resource Packs" I'm not sure if this is a bug, i just need help. We have been working on something on the Realm. We tried using a Backup. It still doesn't work. Any help would be nice. We can open the world that's it's on. But we can't open the realm itself