Hi Xenios,

I think I solved the problem. I started with an image in LPS orientation, then changed to PSR to create the surface file. I accidentally saved the .sur file after I had transformed the image back to LPS, so it would not open as an active surface in PSR. If I load the .sur in LPS, then transform to PSR, the .sur file is functional.

Hopefully my mistake can help someone else in the future!
Cheers,
Sandy