dual extruder merge won't merge

[sasabs]

This problem is with models I make in sketch up or thingiverse .  I enter the two .stl files, generate gcode for each. Seems fine. The merged gcode file is two bytes.

What am I doing wrong? 

[Ryan Carlyle]

Simplest answer -- stop using RepG and switch to Makerware, at least for dualstrusion. RepG is unsupported, obsolete software.