No reference ID created for Amazon FBA shipments, ideas?

We're not able to create FBA shipments as Amazon will not generate a reference ID on an FBA shipment. We've already shipped out one order of 8 full cartons before realizing this, and Amazon did not process them and reached out to about the missing reference ID. However, since then, we have not been getting any reply on support cases as to why this error occurs.

I was hoping someone had the same happening to them and knows a fix. As we've already lost those 8 boxes worth £10k retail value and are getting no replies in our reimbursement case. We do have proof they arrived and labeled them correctly using UPS labels.