When you open the file for the 1st time, if you pick the Material Preview or Rendered mode from the Viewport 3D Shading options, your model might render in a pink color, which shows that the textures aren't linked to the file:

To relink the textures, goto File > External Data > Find Missing Files, and pick the folder where you have saved the textures you downloaded, either the 2K or 4K versions:

Wait a few moments and the textures are relinked properly. After doing this operation, don't forget to save the file.