Stuck in the settings for a world/realm

While I was in the settings for one of my Realms I was downloading my world to back it up but then I couldn't get back to the main menu!

I got an error message that I couldn't bypass which reads:

This world uses a resource pack or template that cannot be used in cross-platform multiplayer.

This is NOT the first time I've had a problem with something I PAID for from you! I'm REALLY starting to get annoyed with problems I'm having with your products!