Well this is frustrating. It just solved itself. No reset, nothing. Just checked and it says 5GB available. But it was like this before, I expect it at any moment to say "not enough storage space" and check settings and see that 5GB at 0 again....
Sorry to bump and old thread but this exact thing is happening to me.
I deleted over 3 Gigs of pictures and videos and it was fine for a while but then the not enough storage space thing started again. I have not used up the space so I have no idea what is going on. Turning it off and also...