Gem Cut Studio uses planar geometry. If you import a mesh from Blender that uses curved surfaces, the verification will fail immediately. Real facets are flat; verified models must be flat.
This occurs when the crown angle is shallower than the pavilion angle by more than 15 degrees. It creates a "dark halo." Verification requires the angle ratio to be within the "Tolkowsky Window" (or a modified window for fancy cuts).
Some sellers take a screenshot of an unverified design and manually paste a verified badge using image editing software. Always ask for the raw .GEM file or a screen recording of the Verification Suite running in real-time.
Older versions of Gem Cut Studio (pre-v4.2) had a weak verification system. Only versions 4.2 and above use the new "Quantum Ray" engine. Ensure the verification timestamp is recent.