In 1.10 you need to download the world template for market place worlds you already created for a "add-on update" even if the world doesn't use addons or resourse packs

How to reproduce:

Download a market place world template

Create the world

leave the world

go to settings

go to storage

Locate the world template

delete it

go back to the world screen

try to go in the world

Youll get the message in the image