I'm having this same issue. Successfully sent request only to find out that the spouse had a new email address (and no access to the old one). Voided the first request and have now burned two more charges trying to get it to work. The only way the "next" button isn't gray is if I delete the spouse from the envelope request.

I'm resorting to paper, but really, it should not be so difficult to fix an email address and re-send the envelope.