A hard bounce status most likely means that one or more of the recipient's email addresses are incorrect and the document hasn't been sent.
When this happens, there are two options you can take:
You can create a new version of the document and edit the recipient with the correct email. (recommended)
You can add a new recipient with the correct email and after that, recall the signature rights of the incorrect email (Note: The recipient whit the incorrect email will still be on the recipient list as Only view)
You can send the document link to the correct email address.
Good to know: Check so that your email client does not filter the emails coming in, this is often a prioritized inbox that is set, then you need to filter to show all emails. Also good to check your spam/junk inbox.