r/AffinityDesigner

I'm new-ish to Affinity v2 and frankly didn't have much experience clipping or masking in Illustrator anyway. I have a large 2-layer background (a colored background with diagonal stripes on top) that I want to clip/mask to a certain size (I'm going to need to have different sized shapes for different collateral pieces). I've grouped the 2 layers. I've created a rectangle to the size I want to use as a clipping layer or mask. I've tried grabbing the rectangle layer and moving it above and below the grouped layers. It doesn't seem to be working. No masking, that I can see. I'm at a loss. Can anyone help me out?

I have two top level layers. I hid one to export the other and it works great. When I hide the 1st and show the 2nd and repeat the steps to export as PNG, i check the preview and see it is blank. I have the area set to whole document.

I'm just trying to export the document with visible content as a PNG image and save to photo library. Working on iOS. I can't figure out why it works for one layer and not the other.