You should receive your One-Time Password (OTP) code on your phone shortly after submitting your mobile number. Make sure you have entered your mobile number correctly. If you have not received the OTP code after waiting for more than a minute, you can request a new OTP code using the 'resend' button that appears on the verification screen.
If you are still unsuccessful after several attempts, wait for an hour and try again. If the issue remains, submit a request using the contact form.