"Import entry number incomplete" message in the Status column of some shipments

Hello,

In the “Shipments” tab under “Shipping Queue” in Seller Central there is a message displayed in red letters that say “import entry number incomplete”, in the Status column of certain shipments.
This suddenly appeared during last night, and this is the first time that I see this. I have received no email or information from Amazon about the necessity of adding such thing as import numbers for my shipments.

Anyone having the same messages?