Can't reach MediaCenter interface after Upgrade

Yeah, I assumed that Sam had read your first post. I see that you already tried the fix described by fzinken.

AFAICT, this is indeed a weaknes of the hack/workaround, which works for boxes that are truly headless – and therefore don’t need a working display.

Take a look at this post: FYI...How I Fixed My Own Post v19.1 Problem and see if it helps.