The obj needs to have material zones for you to apply textures to it, or more to the point for Poser to recognize that it can accept materials.
Import your obj into Poser (File:Import), enter into the Material Room, with the eyedropper selected can you click on the obj anywhere and a material appears in the panel?
Can you click on material along top of panel and see a list of materials?

If I am talking greek to you just open Poser with a standard Poser figure and do the same thing, you'll see materials appear that you can tweak and/or change.

How are you importing your obj into Poser, wavefront obj or 3ds max?

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