Thanks for the replies and suggestions, all. Uninstalled and reinstalled paint.net this morning, and everything works now. Seems to have been a borked update. Only answer I can find to this. 🤷♂️
Just to clarify (especially in case it will help someone else), I tried/checked the following.
1. Yes, it was the active layer, and it was on top. I should have expanded my screenshot to include that. I tried rearranging the layers to see if the order was somehow borked. Also checked opacity was set correctly in the layer properties. No joy.
2. I tried copying/pasting as a new layer directly to my target image from the Windows Snipping Tool (which I usually do). I was able to copy/paste into a new image from the Snipping Tool (image at left in the three at top of my screenshot). Tried to copy/paste from that image into a new layer in the target image. No joy.
3. I tried Ctrl+Shift+V to paste into a new layer, as I usually do. When that didn't seem to work, I added a new layer manually and then tried to paste into that new layer. I tried by keyboard shortcut and from the Edit menu. Still no joy.
4. There was definitely data in the clipboard, as I was able to paste the image into an email, a Discord message, and a new image in paint.net.
5. Tried starting from scratch again this morning with new images. Still no joy. Uninstalled and reinstalled after that.
No noticeable software issues outside of paint.net during all of this, including extensive time spent yesterday in Blender, Movie Studio 17 Platinum, Audacity, and DaVinci Resolve.
System info:
OS: Windows 10 Pro
Processor: Intel i7-8700K CPU @ 3.70GHz
RAM: 64.0 GB
GPU: GTX 1660 6GB
All drivers appear to be current.
Again, I don't know what caused the issue, just that uninstalling and reinstalling appears to have fixed it. 🤷♂️
