If a rig's textures aren't displaying properly, there are a few things you can do to fix the issue.
The first thing to try is to press the 6 key in Maya to set your viewport to textured mode.
If you do this and the rig turns grey or white, or if the scene is rendered and the rig displays as black, the most likely cause is that the texture file either hasn't been downloaded or has become disconnected.You can find a couple of solutions below:
Downloading the Textures
If you're using the Artella Drive (My Files area), the first step to solving the issue is to make sure you have the texture/textures downloaded. The texture file should be included in the same folder as the rig.
Reconnecting the Textures
If you have the texture file but it is still not displaying properly in Maya, you will need to reconnect the texture in Maya. To do this, go to "Window > General Editors > File Path Editor", select the texture path with an X in front of it, hit the "Repath Files" button, Browse to the location on your system with the textures. Finally hit the Repath button and the texture should be re-linked. The rig should have the proper texture again when you hit the 6 key in the viewport.