After I got a warning about my data usage from T-Mobile my shadow app randomly stopped working on my pixel 2. It worked completely fine and I was able to stream No Mans Sky at Ultra detail with little to no lag. And I was exclusively using my unlimited cellular data no wifi.
If you can connect to wifi and the app launches then it might be your provider blocking ya.
So we need a simple VPN Proxy to stop this from happening.
I downloaded Tomato VPN, it's free, no credit cards or purchases was needed for me to use it. It gives you an hour and a half of free VPN and you can add additional time by watching an ad. (Which if you do repeatedly you'll have hours upon hours of connection.)
After downloading and running the app, you can choose were you want to be connected too. If I where you I would look at your shadow PC account and find out which location your shadow is located and match it to the VPN. (Ex. My shadow is in Chicago so my VPN is also set to Chicago)
After doing this I was able to launch the app just fine and the VPN only adds another .2-.3 latency (provided your connected to the closest servers).
Have any questions just let me know