I downloaded airport KMSY (New Orleans Int. ) and had no jet bridges at all, no gate. I was in the FBW A320 using GSX. I had no external power, even though the light was lit saying Avail, but could load the fuel, and passengers. Do External power work because of the jet bridges? Also, when you download an airport from FS2020, do you have to do anything else.
You probably hit the limit of about 1000 SimObjects MSFS can render. Try disabling GSX jetways so MSFS will use vanilla models. AFAIK they are not limited or the threshold is much bigger.