I bought a gopro hero (original one) from Amazon, and I don't know if it's charging or not?

When I put it on charge a red light comes on, I had it on for over 12 hours and when I look at the battery on the tiny screen it only looks as if it's at the first point out of three. I thought I read it takes 4 hours to completely charge up, if this is true why is my gopro not charging up? Thanks

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