If you have entered all money in transactions (money from customers), and all transfers to your current account, then the balance should certainly be 0, unless you have money pending transfer. The fact that it’s a negative balance would suggest that you may have missed one or more money in transactions.
Are you able to pull a report from your card provider, similar to a bank statement? Reconciling your account on QuickFile would be a good start to try and identify any issues: