Worked for us.

Booked an M class ticket using 50k skymiles + a little cash. Suggest taking a screen shot as you book. The itinerary clearly indicated that it was a refundable fare in the screen shot.

Tried canceling/requesting refund online several times but it never worked so I had my wife call in to the medallion line since this was under her name (my miles as a PM are more valuable to us than hers as a FO so we used hers). First rep said that it couldn't be refunded. Odd.

I think, but am not sure, that the fare class on a pay-with-miles itinerary changed from M to something else. I don't have the reservation any more so can't confirm it. This may be why the rep said it couldn't be refunded.

After I showed my wife the PDF that indicated it was refundable, she called back and the second rep said it was refundable (w/o having to make any fuss). They did mess up by converting the entire fare into an eCert rather than refunding the cash portion to my credit card. We book enough that it makes little difference to me though.

Good hint. I hate the conversion rate but I'm trying to put my wife on some revenue tickets (possibly hitting GM this year) instead of all awards and this is useful. Thanks to the OP!