I've been having a similar problem. SiriusXM works fine when on WiFi in my garage, but when on cell data, it never streams. This behavior started with the 2.1.3 update, and continued when I updated to 2.1.10. I have talked to Customer Service, who seemed to think this was a new problem they hadn't seen, and said they would tell the developers and get back to me. A week later, I haven't heard anything more.
This is particularly aggravating because streaming audio from my phone has also become very unreliable. When I got the car almost a year ago, I used bluetooth to stream audio from my phone. When CarPlay was released, I started using that instead. But now CarPlay has become unreliable, and often craps out. And bluetooth steaming will not work from a phone that has CarPlay enabled. Today I ran errands in total silence because the in-dash apps wouldn't stream, and CarPlay wouldn't initialize.
One other problem appeared at the same time that this did (the 2.1 update): Alexa no longer works. When I press the steering wheel button for Alexa, I get a red bar instead of the blue one and she doesn't listen or respond. This was how I opened and closed my garage. Now I have to use the wireless button for the garage door opener, or the app on my phone, while already in my driveway then wait for the door to open. I could ask Alexa to do it while still a block away.
Is there a way to go back to 2.0.79?