That's very strange that you can't select the file, while other .lua files are selectable. Since it has the same file extension as the other Lua filter files, the OBS scripts file loader should allow you to at least select it and try to load it. Did you remove the previous instance from the scripts list using the "-" button? Actually, you shouldn't need to do that if you overwrote the previous filter-PZR.lua file in the folder with this new version. It should recompile the new shader when OBS is opened.