What happens when refund is not approved?

Just to clarify, did you receive an email saying that your return was rejected or did you receive a message saying that your actual refund was not approved? 

Please click What is a refund offset? and What does Rejected mean? to learn more.

Yes

If your return was rejected, you should receive an email explaining the reason why it was rejected along with instructions on how to fix it. For concerns about why your refund was not approved,  you may want to reach out to the IRS. Here's the phone number: 1-800-829-1040