Fortnite illegal restart what does this mean?

I received a notification about illegal restart. I was warned. Unfortunately I don't know what counts that was think not on purpose do you know what counts so that I don't make the same mistake again.

For example, using an account with someone else.

At least that's what it says on Reddit.

My bro is still playing on my account but how should they know that we're playing on an account somehow makes no sense

, does he use the same internet connection as you?

Yes

This includes when you change your teammates in the middle of the cup and start over with them.