Used 2 certificates this thursday, done by a agent living near Chisholm. Got the first "Your Flight Receipt" 1 minute after booking and another one this saturday (2 days later) showing me up front. After seeing this thread i checked my wallet and my 2 used certificates show closed under status.
"My Receipts" show 2 receipts of the same trip. One in economy and one up front. That tip is end of August/beginning of September (65/71 days before departure now, wouldn't call that 'a few days before travel').

Give it two days or if you want call them and ask the Delta agent to please issue the ticket.