This happened to me as well -- family of 4 with two kids under 10, (seemingly) upgraded using miles + cash for MCO-PHL in several weeks from MCE to F. This happened two days ago. Today when I logged in we were sent back with no seat assignments. The EXP agent I called cited the systemwide glitch.

All I asked for was our MCE seats back and she wasn't able to do it. She told me our seats would be assigned at the airport and asked if that was ok. I said I wasn't happy with it as there are very few open seats on this flight and they all seem to be random middle seats scattered about the plane, and that it is not really a good idea to separate a 5 and an 8-year old from their parents. She said glibly to "just keep my fingers crossed for the miles + cash upgrade". Are there any other avenues that I can explore? I don't use Twitter