If you’ve turned on two-step verification for one or more Google accounts you’re having, then you should know, you may get into trouble when you don’t receive verification codes via SMS to your mobile phone, this prevents you from entering into your Gmail account. If you’ve downloaded or printed backup codes, then you can use any one of those to get into your email account.
Otherwise, the best option would be to contact your
service provider telecom operator after waiting for half-a-day to ask why you’re not getting 2-step codes from Google, and ensure there is no problem from their end. The last option is to contact Google by choosing ‘Ask Google for help getting back into your account‘, this takes more than 3- 5 business days.
To avoid this trouble in future, print the backup codes, which you can use when you don’t get verification codes to your mobile phone by visiting https://accounts.google.com/b/0/SmsAuthSettings,
Using backup codes
When you don’t receive the SMS, click on ‘Try another way to sign in’ (check picture 1) and choose ‘Use a backup code you received from Google’ (check picture 2 above) to get into your account.
Google recommends two-factor authentication enabled users to print backup codes.
Backup codes are especially useful for people who travel, have problems receiving SMS or voice calls, or cannot use the Google Authenticator mobile app.”