Why is my alphasmart Neo2 telling me that my files are overused?

Why is my alphasmart Neo2 telling me that my files are overused?

Hi. I just bought an alphasmart Neo2 from Amazon. It worked wonderfully for the first two weeks but then it was difficult to turn it on, and now it keeps saying that my files are overused even though I’ve only written 2000 words on one file. I haven’t even used the other files. Now I can’t turn it on.