There may be apps that are not compatible with the beta and have not been certified, yet, and therefore are not able to be installed or used with full functionality during the beta program.
One UI Beta Team
I have this issue but they won't update over cellular. When I turn wifi on it goes. If I turn a VPN on my cellular it goes. It's not the settings. I've set it to download over cellular. If it were set to download on wifi you get the message 'waiting for wifi' I instead get indication on the app list page that it's downloading and then the individual app page says waiting for download.