Specify New Work Plane - doesn't work?

[bnelson.188587]

I attached some beam systems to a work plane "x". I need to change them and have created a new work plane "y". When I click on my beam system, go to edit work plane, and try to specify new work plane - only ref planes "a", "b", "x" show up. I have about a dz. different ref planes in addition to "y". Can anyone tell me why they do not show up in the pull down menu and why I can't change my beam system from one ref plane to another?
I've tried "disassociate" and am not getting anywhere with that either.
I've already had to scrap and re-draw this all once. I thought there was a way to change this without having to start over every time a slope changes.
Fyi - all my planes are named and I've tried actually rotating the ref plane line more than once, it doesn't work.

[Steve_Stafford]

You can't reassign the workplane if the new plane is not parallel to the original. You can rotate a reference plane so you could move the reference plane to a "known point" of reference, then rotate it using that as your origin for rotation. If you can't do that for some reason like the reference has other things associated to it that shouldn't change then create a new Reference Plane that is parallel to the original, reassign the workplane and then rotate the new one.