Error code: 40050000

It's a server-side issue. The only thing you can do is to backup your original save (if you're playing on PS go to settings and copy it to a USB or use PS+'s cloud saving feature) and start again, that's the only way I've seen that properly works to play online again.

This error has been around for quite a while now... So I don't know if it will be fixed.

PS: Your save is fine.