The Missing Files message can occur in the following instances:
When you import files into Twinmotion.
When you open Twinmotion projects.
When you merge two Twinmotion files together.
When this happens, it means that Twinmotion can’t find one or more resource files referenced in the scene, such as texture maps for materials or custom decals, or IIlluminating Engineering Society (IES) light files.
To resolve this issue, click the Open button and select the folder that contains the resource files.