EVA Construction/Cargo Parts Issue?

[Scarecrow71]

I have a probe core/service bay on the Moon in KSRSS that I'd like to place some solar panels on and use it as a ground antenna of sorts.  No big deal, right?  I send up a lander with an engineer on board, and I place a bunch of parts into a Seq-9 cargo storage part, and land on the moon.  A rather fair distance away from the probe core, but I've got a rover up there too, so I'm going to use the rover as a makeshift car to get to the lander, grab the parts, and then drive over to the probe core.  Should be no big deal...

...but no matter what I do, I cannot get the parts out of the Seq-9.  I've clicked the crane icon, hit "I", right-clicked on the cargo container.  I can, at times, left-click on the part I want, but then the game wants me to place it into an inventory instead of dropping it on the ground for construction (I'm going to "attach" the parts to the rover for driving it over to the probe core).  But I cannot seem to get EVA construction to work no matter what I do.

What am I doing wrong?  Everything I've read says you should be able to left-click on the part in EVA construction and then just drag it out of inventory.  But the game won't do that.  Can someone please help me here?  I'm ready to just send the engineer home, lose all the parts and the probe core, and give up on EVA construction at this point.  I've got an image of the scene:

Now, before someone says "Hey, the engineer needs to be closer to the cargo container":  I've tried this from the ground, on the ladder, and standing on top of the lander.  Nothing - NOTHING - I've done works.  I need help before I give up here.

[DennisB]

Make sure, your construction mode is "place". I had that issue, that nothing happened, as the construction mode somehow switched to "rotate",  and the kerbal tried to rotate the storage unit, which was impossible, but then I got a message, that the part can't be edited.

[Scarecrow71]

Of course it was the obvious "check to make sure you are in part placement mode".