Same issue on HK from this morning and now too, and I asked my VN team, they can access the appstoreconnect and publish app to testflight group, it seems that region issue on the appstoreconnect today, currently my VN team help operate apple store first

I found I tried on the mobile browser Firefox with cellular data, and can access the page normal now, but I hotspot to my macbook, still same issue, so weird!!! currently I use the mobile browser Firefox to check the apps :(

Issue resolved now on HK, refresh the site and become normal