Hi there. I got here a set of steps to help fix error 324 in QuickBooks Online (QBO).

In QBO, error 324 indicates that the program cannot find the account you set up when it attempts to connect to your bank or credit card's website. These may be caused by the following:

• The bank or credit card company has changed the account or moved it to a new server.
• The account name or other details on your bank or credit card company's website have changed.
• The bank or credit card company issued a new account or credit card.
• You closed your bank or credit card account.

To resolve this, you have to update your connection. Here's how:

1. Log in to your QBO account and go to the Bookkeeping menu.
2. Next, select Transactions and click Bank Transactions.
3. Then, select Update.
4. If you still see the error, look for a banner on the Banking page. Select the Check Connections link and follow the steps to fix the issue.

If you have a new account number or new credit card, you can refer to these steps in fixing the error. 

For reference, check out this article: Fix banking error 324.

It's also recommended to reconcile your account regularly to ensure that the balance matches your real-life bank account. 

I'm always here ready to lend a hand if you have other concerns managing your bank accounts in QuickBooks. Have a good one and stay safe.