The new delta.com won't let me change seats. For example, I'm on a flight in 6 days and the DM/PM upgrades have just cleared, leaving open seats in EC (I'm booked further back in the plane). I wanted to grab a seat in EC, but I keep getting the following error message:
One or more of your requested seats are no longer available and could not be assigned. Please review your current seats and reselect if desired.
Message#SEA0002
This same message popped up last week; I was unable to change seats while logged into delta.com; amazingly, I was able to do a seat switch on my I-phone using the Delta app.