There is no Sub Rosa 23. This is the latest post that I’m aware of on “issue 23”: Did Sub Rosa publish anything after issue #22? - #11 by Ben_McFarland
That being said, Timothy Ferguson infered in Mythic Europe Magazine : Call for Submissions - #20 by Timothy_Ferguson that he had been supported by Sub Rosa. My guess is this would be the transfer of unpublished content (but it could be just advice), which would point in the direction that work stopped and won’t resume. This is just an informed speculation, and of course the authors might change their mind some time in the future and resurrect the fanzine. But the only currently active fanzine as far as I know is the one published by Timothy Ferguson.