The Crosspass app requires a real device, not a simulator. Here is an excerpt from the white paper that explains the reason,
--snip--
Although the number is very small, people who use custom Android ROM is likely unable to pass such check.
Once we implement CAPTCHA for the cases when many phones appear to come from the same public IP (I saw this with a Telecom in South America), I can make it that if the device is does not pass the Play Integrity check, the server will also request a CAPTCHA.