My latest reply from seller support was (this seems to conflict with what other people are being told!!)
Thank you for writing to us with more details on the update request.
I have investigated the details and understand that there has been delays in Shipments being received at the fulfillment center. We have contacted the fulfillment center and they have informed that this is due to the peak season the Shipments are being sent and the teams are working continuously to receive and add inventory as soon as possible.
Shipments cannot be directed to other FCs are also busy receiving and inventory from Shipments. The shipments are aligned with FCs basis the type of product, size, category etc and hence specific FCs are aligned.
We have already notified the FC and they have informed that they are working double to add all shipments as soon as possible before the festive. We request your understanding and co-operation while the teams are working to providing a resolution on Shipments as soon as they can.