No VGM, no load: a container without a submitted VGM is rolled. The weight can be obtained either by weighing the packed container (Method 1) or by weighing the cargo and adding the verified tare (Method 2), and it has to be filed before the carrier's VGM cut-off. Missing that cut-off is a routine, avoidable cause of a box being left behind.
Glossary
VGM (Verified Gross Mass)
Verified Gross Mass, the total weight of a packed container (cargo plus the container's tare) that the shipper must verify and submit to the carrier before it can be loaded. It has been mandatory under the SOLAS convention since July 2016.