This system is definitely different to the Acadia listed above, as that is manual retraction, the Equinox is electric retraction.
Ok I just had this problem and (hopefully) managed to fix it. The white clips have a wavy end on one edge of the clip, that goes at the top, and pushes in to the rail that the black plastic part is attached to. So you have the shade folded over on itself, pull it past the black plastic part and slide back into it, then reach behind with the white clip and push it onto the back of the black plastic part in the direction of inside the car to outside the car (I hope that makes sense?) it should then clip into place firmly, do that on both sides and test full retraction. The photo is a bit hard to understand but that's how it should look from above when fitted.
This should not take a dealer more than 10 minutes and not hundreds of $$$, if I can figure it out with no trained mechanical knowledge. View attachment 18560