For security purposes, we are not given the reasons for authentication failure or why they would not be eligible since KBA is through a third party. It is possible that LexisNexis (the provider that pulls the information for KBA questions) was unable to gather enough data for a full profile on the client.
In this case, the taxpayer would need to manually sign the returns and upload the documents into SSR or email/fax them to the firm's office. The taxpayer will be given this option after KBA is failed. The return does not need to be re-called and re-delivered; it will automatically revert to a manual signing option for the taxpayer.
Where do KBA questions originate from?