For some reason, whenever I start the Shuttle now, it tells me that "no GPC is assigned to display output".
What mission phase do you try? What state is the DPS management option in? What state are the GPCs in? Are they actually able to output?
As far as I remember, the check is only done when DPS management is in realistic, so something is weird here.
And, again - what exactly did you do to cause this state? I have not published any instructions how to turn off BFS (and this is in fact not simple and definitely does not work in OPS 2) - so what instructions did you follow?
(Even if some config file is stuck for one mission phase, it's unlikely to be for others because FG sees different mission phases as different aircraft).