I am in developing application for Android smartphone for make WebAuthn authentication using FIDO U2F protocol by NFC interface. For reference purpose I use Yubikey 5 NFC Token. The application creates virtual token and support FIDO U2F NFC protocol Specification v1.0. My application was tested on some demo sites such as https://webauthn.org/, https://demo.yubico.com/webauthn-technical/registration, where registration and authentication goes correctly with my application. Then I test registration and authentication at mail.ru post service and also all is correct.
Finally I turn on 2-step verification at Gmail and successfully register both Yubikey 5 NFC Token and my application virtual token. Then I try to use both devices to pass 2-step verification. When I using Yubikey 5 NFC Token at 2nd step of authorization it goes correctly, after dialog with "OK" mark I click Next and enter to Gmail account. But my application fail authentication in very strange manner. After my application reply to authentication command and Gmail dialog window show "OK" mark, I click to "Next" button and no enter to Gmail account happens. Below 2 screenshots of this process.
Dialog with "OK" mark:
Dialog with unknown problem:
Because of no any extra info about problem, I have no idea what is comes wrong and why after dialog with OK mark I can't enter to Gmail account. Have you any idea about this problem or how to get extra info about reasons of fail?
Extra information: I also checked my virtual token application to work with fastmail.com e-mail service and both registration and verification is OK. With Gmail it seems like it check some information in attestation certificate when make 2nd step of verification. If this true, I need to clarify what fields in the certificate are cheked.