I got through to tech support this morning. The problem started Tuesday and they've been working around the clock since then to get it resolved. They intentionally removed RR Boxes from the PM choices because there's a bug that is causing incorrect labels to be generated. Rather than let people go on paying for labels and getting bad ones and having to make refund requests, USPS elected to remove the option until the problem is fixed. As of 8:45 a.m. ET this morning they have no idea when that will be.
