I had the exact same experience yesterday. We also check in on Dec. 1. A few things were different on MDE:
1. The online check in option appeared. Easy to navigate, took care of that.
2. Clicked on "Manage magic bands" and it took me to a new page prompting me to customize. Each person in our party had a section to select the color (which automatically previews with the new color) and an option to revise the name (default is the reservation name in all caps). After customization is done, you are reminded that you can adjust customization until the 30 day mark.
3. Clicked on make FP+ selections...no luck . Half the time I got the old "link up family and friends" rejection box. But sometimes I was sent to the actual selection page. Unfortunately, the default was October dates, and I got an error pop-up, saying that the dates are not in my range. No option to adjust dates...what a tease!
DH called to inquire last night. Was told to just keep trying across the next few days . Will keep you posted.