The issue is, your description of the problem sound exactly as it was, for a very short time, BEFORE today's update. Do you see bags/container being loaded ? If no, then you don't have the latest version so, run the Update again.
Of course, before posting, I tried the reproduction sequence you reported here, that is just Boarding and nothing else, with two different airplanes:
- The default 737 imported from FSX
- The QW787
In both cases, Boarding completed normally.