For security and enforceability reasons - Declining, Voiding, or Completing an Envelope are all hard actions in DocuSign. Any of these actions will complete the envelope, locking it down for any future changes.
So basically there's nothing that you can do to resurrect the voided document. You need to resend it back out for signature. Which makes sense because you don't want to be able to apply a signature to a form without a signer's knowledge (i.e. fraud). I know in this case, they've already signed the form in question, but if the reason for voiding invalidates the form entirely most senders want to know that the document is completely dead without copies containing signatures being out there somewhere. Even if you could get a developer to remove the voided watermark for the partially completed document, it would also remove the security token validating the already placed signatures, making your document indefensible legally.
All you can really do is CLONE the envelope and resend it for signature to all parties.
(https://support.docusign.com/en/guides/cdse-user-guide-envelope-management-clone-envelope) Clone an Envelope - Classic Experience
(https://support.docusign.com/en/guides/ndse-user-guide-clone-documents) Clone an Envelope - New Exprience
Hope this helps.