Not possible to help you with so sparse report, missing crucial information like which airplane you are using.
From what I could gather from your report, GSX initially read the correct number of passengers (you don't say what it was, I assume it wasn't 214 ?), but then it was changed when passengers started to come out.
This can happen if another add-on changed the GSX passengers number after GSX read it from the flightplan and GSX always gives priority to the add-on (usually the airplane itself that is integrating with GSX, but it might be any other addon that integrates with GSX) so, if the passenger number changes after GSX read it from Simbrief, GSX will assume the airplane (or whatever add-on does that) knows better, so it will use the new number.
About pilots/crew not boarding, an add-on that integrates with GSX can also cause that.
If you provided a diagnostic log, I could confirm if this was the case, since when add-ons change the passenger number and the pilots/crew boarding preference, it is logged in the log.