I am having the same problem and tried the solution suggested by you.
I do not see any option to 'enter the blackberry world' at step 4 of your suggestion.
Are you trying this through the Music app or the GAmes app.
If you dont find the option in the Music app, try it in the Games app.
i downloaded and installed the updated version of bb10 software and i am able to access BBWorld again.
thanks for your interest and help!
i did it but blackberry world is not work yet