Avatar upload problem

So, I'm trying to make an avatar in blender that uses the appearance sliders (That's a fitted avatar, right?  I don't know if I have the terminology right).  I've weight painted it, and it works perfectly in blender.  When I export to second life, it PHYSICALLY works fine, but no skins will work with it.  it's just a white body.  I was told to upload "materials" instead of "Textures" and I did that, but the result is the same.  One thing I did notice is that the UV map got messed up when I symmetrized the mesh.  The avatar moves fine, and the shape edits and behaves as it should.  I just can't apply textures to it.  I asked the creator of the skin I'm using for help, and they said that when they uploaded it with materials instead of textures, it worked right, but it doesn't for me.  What am I doing wrong?  I can't find any answers to this in any forums or youtube videos.  I've even followed along exactly with multiple tutorials, and the creators don't have this problem.  Please help.  I'm happy to elaborate, or even provide pictures if that would help explain better.  Thank you in advance for any guidance you have.

Hel