I’m currently unable to change worlds both from the main log in page and also when in-game.
When loading up OSRS mobile, I click “tap to switch” and nothing happens, i have then tried to change worlds in game and the interface doesn’t load any worlds and stays blank.
I am playing right now on mobile and I am able to use the world switch feature. Double check if you are using the latest available update iin your Play store/Apple store. If that is the case; have you tried removing/deleting the mobile client, restart your phone and re-download the application? This does wonders
I would also suggest taking a look at their FAQ if you haven't done so already. It contains lots of useful information regarding all things RS mobile.