Path won't fill in my document but fills if pasted into another document.

Using the pen tool, I have created a path.  It will not fill, despite the fact that it is a positive “Combine” shape and is a completely closed path.  If I copy and paste it to a new document, it fills just fine.  Paste it back into my working document, and it won't fill.  I have another path near it, on the same layer, which is filled.  I've tried using "Combine Shapes" to make sure it's a positive shape, I've made sure it is on my top layer, I've made sure the fill color doesn't match the color behind it.  This has happened before.  Windows 11 Pro, updated; all drivers up to date; Photoshop 27.5.0.