Second signer failed to receive document

My documents need to be signed by several people. I'm finding out that some of the forms are not getting to the second signer after the first person has signed or they are getting signed and it's not getting applied. I tried replacing the second signer with the second signers email address again and Adobe Sign wouldn't let me do this. Is there a way to resend the form to the second signer after the first person has signed it. And why is this happening?