FYI, since ordering Magic Bands has more to with resorts than the theme parks, I moved your thread to the Disney Resorts board.
To answer your question, Disney has suspended MB ordering/customizing during the closure. Although similar to the next poster I was able to customize MBs for a summer trip yesterday (not sure if a fluke or what).
Here’s the current language from the closure update page on their website, FWIW.
MagicBands
If you have placed an order and received notification that your MagicBands have already been shipped to your home, you will still receive your order.
If you have arranged for your upgraded MagicBands to be delivered to you at your Disney Resort hotel for an arrival date from March 20 through the closure period, your order will be automatically cancelled and you will receive a refund of the amount you paid for the MagicBands.
While the Walt Disney World theme parks and Resort hotels are temporarily closed, we are not currently accepting new MagicBand orders linked to Walt Disney World Annual Passholders or Disney Resort hotel reservations.
Hope that helps!