Email Notifications for Signatures Not Sending

Hello, 

When I send a document out to get signed, the recipients aren't receiving any emails to sign it. I tried replacing a recipient with someone else, the new signer did not get an email but the old signer got notification they were replaced, but never received the initial email for signature. 

All junk/spam folders have been checked and email settings have been checked to ensure that the emails are not going to the wrong place. 

Thanks