I've just popped into my YouTube account to see if anything has chnaged, as I'm still getting the error on ReStream and OBS that it wasn't detecting my YouTube account as enabled for live streaming, when it has been active for a while.
I attempted to go live directly on the YouTube desktop site and was given a message saying that I requested live streaming today (1st August) and it will take 24 hours before I can stream. I'll check back tomorrow, as this may be the hidden step to fully enable live streaming and alllow ReStream and OBS to connect to my account with streaming access.
I'll update tomorrow when I find out...