Put the summary of the bug you're having here

Also when I play multiplayer, my player only moves a little bit, then stops. My CPU and RAM usage is fine and everything is on time in the chat and in
the inventory.

What I expected to happen was...:
I would be able to select the world and start it up

What actually happened was...:
Nothing

Steps to Reproduce:
1. Click on singleplayer
2. Click on a world