I cant replace my world for my realms.

            When I try and replace the world with a world that I already have, It says " Exporting world " with a loading screen and then when it reaches the end it goes to a screen that says " analyzing Upload ", and it just stays there until I quit the game, or it will say " try again later, and check your internet connection. " I check my internet and it is fine. I also, tried to uninstall and reinstall the game to see if that works but it just says the same thing over and over again.