IOS device cannot connect to realm

I was trying to connect to my friends realm, however when I clicked the button to join it gets stuck on "Loading resource packs". It stays like this until the connection times out or, if I click the cancel button, just says "Unable to connect to world", then takes me back to the main screen. Sometimes I can get lucky and it will let me on. After about 30 seconds, it will disconnect me and I will be sent back to the main screen.