Doesn't sound like you broke it but you might have to pre wind the spring before you put it on or it has to be put on a certain way in order for the spring to catch and start winding. You will just have to play around with it a little and see what works. Patience will be your friend!!!

Likely the end is bent or broken. How you repair depends on what engine you have. Model numbers are helpful.

I agree with Tomplin, sounds like when the old cord broke the recoil uncoiled with enough force to snap the hook end off, or the force was strong enough to bend the hook end and now the spring is no longer able to wind. Make sure that the cord diameter is the same as what Toro specifies, if it's too thick it could take up too much space inside the reel and bind when it's retracting.