BoltBait:
I located you and 4 others who also have plug-in packs from this website: https://www.guidingtech.com/paint-net-plugins-2019/. I know a good bit about how to go into C Drive to run my older design software in Compatibility Mode... However, these files are strange to me and not all of these packs came with Installers. Only 2 that I could locate. Yours was the only one recently updated. Most were last updated 2014, 2016, 2018. I'm honestly uncertain about both folders (FileType, Effects) and wonder if there are a few which belong in the opposite file!! I can't email you, but could you email me with "Verifying folders" in the Subject line so I know it's you? As you are a coder and moderator, I know you could look through both quickly and see anything that might be in the wrong folder.
My email is: <snip>. I would appreciate this small kindness and would gladly pay for your time via your Donate button if you could get these two straightened out for me. Let me know if you have the time to do this favor. Thanks!
~Laura Shinn Designs
author/designer/formatter