Common issues with the asset displaying wrong or different from the marketplace previews
Mesh Distance Fields not Enabled
A lot of our assets use Distance Fields for their materials, which UE4 has disabled by default.
You can easily enable it by going to your project settings and searching for "Generate Distance Fields" then enabling the checkbox "Generate Mesh Distance Fields"
An engine restart is required.
In some cases, even with Mesh Distance Fields enabled they still do not get generated. A common issue is because there isn't at least 1 static mesh in the scene. You can fix this by simply dropping a cube somewhere within your scene.
Another reason could be that you have set your engine scalability "Shadows" setting to medium or lower. Distance Fields require at least High "Shadows" setting to generate.