Balance won't catch left side of window

When you say balance hook, which part are you referring to, exactly? Do you mean the hook at the end of the cord? If so, it might be an issue with the hole where the hook inserts. Could you also be talking about the top sash guide? These are small, usually nylon pieces that install on the top corners of the sash. If they're broken, the balance will just shoot up to the top of the window after being installed. Let me know!