Check your displacement scale in the Redshift obj tab tessellation / displacement settings. Currently a value of 1 unit in your screenshot. Is that significant compared to the size of your model? If you need to increase it, make sure you also increase 'Maximum displacement' to match, as that is a clamp on displacement value.
Ok. I found out what the issue is/was. I was trying to displace/colour an imported object, which does not seem to work in the same way, as when I create the object directly in Houdini.
See image. Here I have assigned a red colour to a sphere in Houdini and a yellow colour to a sphere object imported into Houdini.
As you can see the colour is assigned to the sphere created in Houdini but not the sphere imported.