[Help] Modelled Detail Mesh Completely Invisible

I modelled some low poly terrain assets and imported them into unity. All was going fine. All the models seemed fine, with the correct scaling, texturing, and normal direction. Then I tried to paint the objects on a terrain as detail meshes. I could not get them to work. They appear completely invisible, assuming they are even there at all. Every single one of them will not appear. I tried zooming way in and out and increasing the detail distance with no luck, so it isn't a scaling issue. I also quickly imported the standard terrain assets and tried painting as details. No luck, although I did get them to work perfectly well as trees. I tried messing with the brush settings and all of the settings in the detail mesh menu. Does anyone know what the problem might be? I think that unity's detail mesh painting is at fault since nothing will work, but I plead that someone will point out something I am doing so that I can fix it sooner. Thanks!