Thats it!
I was not even aware of this GSX function. After activating KLAS in GSX, the jetways are working now.
Thank you for the hint!

I just installed the Las Vegas airport for MSFS2020 and noticed that the jetways are visible / available in the scenery but do not work.
GSX Pro 3.0 is showing 'No jetways here'. I tried several parking spots with jetways, but the result is always the same.
What maybe the problem? Any solution?