After registering an account, S2G sends a verification email to the address used to register. In this email, a link is included which has a unique verification token to continue setting up your account (see how).
It is possible for this email to be delivered to a Junk or Spam folder. If unable to locate it, to reissue an email, go to the login page at https://prod.bidsync.com/bidsync-login/:
Enter the Email Address and click NEXT. On the credentials' page, click "Forgot your password?" at the bottom
Enter in the email address used to register and use the provided link to continue setting up and verifying your account:
There have also been instances where information entered did not get saved properly in the database and behaves as if no registration occurred.
A quick hack to check an individual email is to return to the Basic registration, even if you originally intended for a Pro subscription, and input the email address.
If registration was successful, a popup appears to confirm. This also provides a link to resend the registration verification email if it hasn't been clicked yet: