You might consider that it's currently showing "Temporarily out of stock", and something along the lines of "we are working to get more inventory" on Amazon. At this point, there's no telling when the order will ship or if they ever get stock back in.
ETA - I'd strongly consider cancelling the Amazon order. You can order direct from Singer and both items are on sale. $229.99 for the machine, $39.99 for the walking foot, and they're running a 20% off coupon code.
Machine (4452)
Heavy Duty Crafting
Walking foot (using their accessory finder)
Coupon code is SUMMER20.
Comes to $215.98 plus tax, free shipping.