I downloaded the extension from https://www.illusionofmana.art/Pribambase.html. When I tried installing from the zip file I got the same error as you. I went to the folder where I downloaded the file, unzipped it, navigated to pribambase-blender-windows/pribambase/aseprite. I dragged the .aseprite-extension file into Aseprite and it installed.
I’ve never used the extension beyond this, so I can’t offer any further advice.