It happened to me as well. I got the 5th schedule change on an award ticket AZO-DTW-TPA for a November trip, for which now I no longer had a workable connection in DTW, much less seat assignments. I was lucky enough to get someone in Chisolm on the phone and they got me rebooked, but said that the seat assignment function is not working and they aren't sure when it will be. She told me that all of the mainline flight numbers had been changed, many of the schedules had been changed slightly, and from what they could see, all seat assignments were gone.