Driving Dimension Issue

[designcompany]

I've been using Catia V5 for 3 years. I've always used driving dimensions to position 2D geometry that I have drawn within a drawing view. I understand that, when creating a dimension, you must first click the 3D geometry and THEN the 2D geometry you wish to move. But no matter what I do today, the box is always greyed out. I have even tried using two 2D lines instead of using any 3D geometry. I've tried checking and unchecking "Create Driving Dimensions", "Create detected and feature based constraint", "Allow Driving Dimension", "constant offset between dimension line and geometry", among other things. I even restarted Catia, opened a different document, tried various views. I don't know what the deal is! Any suggestions? Thank you!