If you are not receiving your code, the Yahoo Support site suggests checking the following:
: Check that your mobile plan hasn't reached its data or SMS limit. Verify Code Yahoo
To verify your Yahoo account, you typically need to receive and enter a numeric code sent to your recovery phone number or email. This process confirms your identity when signing in from a new device, resetting a password, or using two-step verification. If you are not receiving your code, the
: Type the code into the "Verification code" box on the sign-in screen and click Verify or Next . Managing Verification Methods resetting a password