To my understanding, in order to get an inp file from GBS you need to supply it with a gbXML file that contains enough information to run a simulation (schedules, material properties, etc.). This is because GBS will take the gbXML and convert it to a DOE2 based simulation and if this simulation fails then I don't believe you are able to grab the inp files. Looking at the OpenStudio gbXML export, it doesn't seem to contain schedules, construction assignment or material properties so I imagine this could cause an error. That said, I imagine you could post process the gbXML file before uploading to GBS in a fairly simple manner to get the information needed (i.e one default material and construction assigned to all surfaces). Moreover, I believe (I could be wrong) there are certain characters that can cause the GBS simulation to crash, but I'm not sure what these characters are exactly.

I don't have a single clue about Green Building Studio, but I thought I might mention a couple of other things related to going from an EnergyPlus model to an eQuest model:

• SIMEB from Hydro Quebec should be able to translate your geometry from an IDF file to an eQuest INP file.

• NREL also created an IDF to INP converter, but that only works for constructions. You can read more here

Note: if you wanted to go the other way round, the BTAP from Openstudio standards is what I'd use. But read this post eQuest Geometry to EnergyPlus too.