Due to high demand and limited appointments, December 15 to December 31 are currently unavailable to receive your products.
Info to other sellers : be advised that due to exceptionally high demand and limited appointment availability during the holiday season, December 15th to December 31st are currently unavailable for receiving your products in some Fulfillment Centers
This is what we received as warning :

Plan your shipments accordingly and consider alternative shipping dates to ensure timely delivery of your products..
Due to high demand and limited appointments, December 15 to December 31 are currently unavailable to receive your products.
Info to other sellers : be advised that due to exceptionally high demand and limited appointment availability during the holiday season, December 15th to December 31st are currently unavailable for receiving your products in some Fulfillment Centers
This is what we received as warning :

Plan your shipments accordingly and consider alternative shipping dates to ensure timely delivery of your products..
36 replies
Seller_9P3NZUhJcAVNo
Hello , I have an FBA order that has a delivery already schedule for 12/24, this appointment was granted on 12/02, would this be affected?, I do not see any comment form Amazon, kindly advise.Thanks
Seller_GpmqM2WPKrGyj
what happen to the box if they arrive between those dates ? They send back the boxes ?
Seller_8Btu9fOsrLqIG
I am very curious about this too. We are trying to get everything in before December 15th, but we were also wondering what happens if a shipment reaches Amazon during this period? Boxes get put aside until January 1st?
Seller_oDXVaydIpi3Hi
Sounds like sellers need to make some metrics for Amazon to continue to allow them to sell the products FBA:
Failure to accept delivery <1% 30 days rolling.
Time to receive products < 90% in 3 business days.
Errors in receiving <1% 30 days rolling.
Topher_Amazon
Hi @Seller_ADNyBcEC0E5lx,
Thanks for noting this here on forums.
High demand has resulted in limited appointment availability for receiving shipments at our U.S. fulfillment centers in December. As a result, delivery windows are unavailable between December 15 and 31, but will resume on January 1. Appointments have been updated to reflect current availability, so we recommend adjusting your shipping plans accordingly.
Topher
Seller_XzqETj5nHwnHH
this is after they told us to buy and send up product
Seller_O1l36ybjBg4zB
Our shipping carrier has a delivery appointment scheduled for 12/23 but we have to update the delivery window on our end to reflect that and can't. Amazon allows us to update the delivery window anytime before the delivery, but now we can't. We had set a preliminary window on the shipment in January but intended to update it in Seller Central based on the actual appointment date the carrier got. We can't update it on our end to match so now our metrics will get dinged. Topher_Amazon or anyone : Do you have a solution for this so our metrics don't get dinged. We always update the window on our end once the carrier gets an appointment.
Seller_HNZZeqk2vOCxe
We just shipped a pallet 2 days ago but 2 weeks ago they would not accept our pallet and we had to break it all down into 10 FBA shipments. BUT Amazon had sent us a notice I think in September alerting us to all of this and told us to ship FBA and AWD before teh end of October if we wanted to ensure our products be ready to go for Christmas. Next year we will ship 4-6 pallets on or before October 31 to be ready to go. Its not worth the risk to be out of stock. :)
JMO but think ahead by 3 months min with Amazon and it will help your business out a lot!!
Seller_ADNyBcEC0E5lx
Hello @Topher_Amazon , thank you for helping us !
Just to be clear, we can use this example :
A shipment was scheduled to arrive at the Amazon Fulfillment Center on December 13th, but due to carrier delays, it's now expected to arrive on December 17th.
Will this late shipment still be accepted and processed by the fulfillment center ?
Seller_4YrdMw2uWOOh3
my box delivered on 10th by fedex, status also updated to "delivered" Still not checked in by Amazon team.