I don't really keep track so I don't know. Lately I've been connecting via T-mobile so everything works.

In general, I've found that flightaware will work fine but when I connect to messaging, it stops.
I assume flightaware whitelisted since it needs to work because UA uses it for flight status.
I assume it stops working with messaging because they are sloppy and only whitelisted the messaging sites and neglected flightaware.
It's kind of hard to test as I've found that all the systems are universally unreliable and slow. I kind of laugh when I see them say that video streaming is supported. I can barely get all the images to load reliably on a website let alone get a video to play. The unreliability might explain the OPs report of flightaware not working. Or it really is a specific platform that doesnt work.