Weed Eater?

I have a Troy Built, I think a TB70SS weed eater with an easy start. (It's the one where I can change attachments) I prime, flip the blue lever and then pull to start. It's worked for months, but then this last time, the string pulled out easily without any tension or even trying to start and then retracts back in. Out and in, out and in, did something come unhooked? This happened one other time and I took it apart, looked at it, put it back together and it worked. This time I wasn't so lucky. :)
Thanks for your help!