What Android version are you using? I think there’s currently an issue with older Android versions. If you have more information you can provide, that would be helpful to figure out the root cause! https://github.com/thunder-app/thunder/issues/178
Looked into it. It's a known Flutter issue with older Android devices including Android 7 unfortunately. Has to do with old expired certs. A work around might be possible though. I've updated that issue with relevant info.