When you drop an OBJ file you should see an import options dialog. If that's not happening something is definitely not right. This is what you should see ...

It seems more likely the OBJ is either too big or too small to see in the preview. First try setting the scale to ...

"100% " and "of standard figure" Set the option "Centered" and "Place on floor". Uncheck all the other options.

You should see the object appear after clicking [OK].

If that allows you to see the imported OBJ it's now just a matter of figuring it's real scale. Poser's scale is very small compared to most other apps. So try scaling to 10% or 1% "of original size". Once you find the right scale just import all the objects at an appropriate scale.

For example Blender scale is 0.382 compared to Poser scale.