It’s strange. Apart for that problem, I call for boarding and no passengers coming. I don’t see them.
Which scenery you used ? Visible passengers require SODE jetways, and I believe there's a clear message from GSX if you are boarding on a scenery with no SODE jetways, about passengers not being visible because of that.
If the scenery *does* have SODE jetways instead, the reason why you don't see them might be related to their number. And again, the FS Labs is different than other planes, since it's supposed to TELL GSX the passenger number, which is firstly set on its MCDU provided the plane has been correctly configured to use GSX and the passenger number is set correctly, because GSX with the FS Labs relies on the plane to know how many passengers you have.
On other airplanes (those that don't control GSX, for example PMDG), the passenger number is either estimated by GSX depending on the payload ( default option ) or you'll see a prompt from GSX asking you to insert the passenger number manually, if the Estimate passenger option is disabled in the GSX Settings.
But again, all of this assumes that, in order to SEE passengers ( on jetways, at least ), the scenery MUST have SODE jetways.
An easy way to check if your passengers are working is to go to a parking in the open. In that case, passengers will use a Bus and Stairs, and will be always visible IF GSX Level 2 is Active, regardless the kind of jetways used by the scenery.
