The message This signing link was issued to a different household contact. Please sign in with their account. appears when a parent opens a signing link email while logged into the portal as someone other than the contact the link was issued to. Each signing link is issued to one named contact of the household and can only be used by that contact's portal account.
To resolve it, the parent logs out of the portal, then opens the link from the email again and logs in with their own account. When the parent does not have a portal account yet, the school creates one for the contact and resends the link from Application Form Invitation with the Send Invitation button.
A link also stops working when it has already been used, when it is more than fourteen days old, or when the school has sent a newer link to the same contact. Resending the link from Application Form Invitation issues a fresh one.
Note: The link only routes the parent to the signing page. The parent can also sign without the link by logging into the portal and clicking Sign on the invitation list. Review Application Form Signing.