Perhaps your client can save a copy of the SU file back a version for you? For example, if the problem is that they are now using SU Pro 2018 and you have Make 2017, then they should save a copy back to version 17 to give to you.
Finally I found the SketchUp Viewer 2018 and it works !
But I remember that the client use Layers (open/close or visible/not visible), but I can’t find the place to open/close the Layers in the Viewer 2018 version.
Can I found the Layers in Viewer version ? Where can I found them ?