The launcher says I can only play offline.I went to singleplayer,I was about to load my world,and it crashed.

Put the summary of the bug you're having here

What I expected to happen was...:
Describe what you thought should happen here

*What actually happened was...:*I went to the launcher,every profile had to be played offline.I load my default profile and loaded my world and it crashed.
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...Load minecraft and go to singleplayer
3. ...Load a world