I'm here to help change the beginning balance of your credit card account in QuickBooks Online (QBO).
When you tried to put zero as the beginning balance, did you get any error messages? If so, may I know what the specific error is? Any additional details will be much appreciated.
In the meantime, you can edit the negative amount showing on the account's register and change it to zero. Here's how:
1. Go to the Gear icon at the upper right and pick Chart of Accounts under Your Company column.
2. Locate the credit card account you created and select View Register under Action column.
3. Click the amount and enter zero, then Save.
That's it! Let me know how it goes or if you're referring to something else by leaving a comment on this thread. I'm only a post away if you have any additional questions or concerns. Take care and have a wonderful rest of the day.