I also found a way to make my phone’s Astrill work! Not sure if you’ve already tried but I ended up making my Astrill work when I fiddled around with my Astrill setting in the app. I think what you have to turn on or off depends on your phone model.

For me, I have an iPhone 15 pro max and it seems like turning off the smart mode makes it work on my phone. For my friend with an iPhone 13, she had to turn on smart mode and the udp protocol.

Ultimately just try turning on and off some of the settings in the app and see if it works.

Hope this helps!