I recently installed SolidWorks 2018 but I'm having a problem with assigning global variables. I understand you have to double-click the dimension, and then use the 'modify dimension' dialog box to assign the variable to that dimension. But that dialog box does not show up...

I tried turning on/off Instant 2D but that doesn't do anything. When I double click the dimension it does the same as when single-clicking it. The property manager window on the left side of the screen opens and I can edit the dimension there, but I can't assign a global variable there.

Occasionaly the dialog box will show up, about every 50th time I double click the dimension.

What am I missing??? This is so frustrating, I just want to punch my computer...