I'm not sure if the free UVMapper is still available, but it's a great little tool if so. That way you can easily check IF there's a UV map on the obj or not.

I've had sort of the same problem from time to time, exporting from Hexagon, which is my modeler of choice. I UV map it in Hexagon, and most of the time, the UV map carries over (anthough usually pretty mangled - but at least I have my material zones ...) - you can also check with Poser's Grouping Tool - perhaps your material zones ha been turned into groups? That way you can grab them and assign a material zone to them.

Poser's Grouping Tool is GREAT. Takes a little getting used to, but once you've got it, it can do a lot :)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.