Epic Online upgraded to full game problem

So, looking at posts from last year; if you buy online version from Epic Games then upgrade to full game at full price you still can’t use RedM?
(I can get on to RedM itseld, see all the servers and start logging on process, Mods say they’re installing and all looks good but i end up with the sepia loading screen with magazine spinning endlessly.
What’s the latest advice on this ?