Thanks for posting on this thread, ra02.

When you're unable to see all of your customer transactions, it's possible that it was filtered on a different type or deleted.

To display of the sales transactions, let's make sure to select All transactions from the Type drop-down list.

Here's how:

1. On the left panel, click Sales > Customers.
2. Select the customer's name and click the Transaction List tab.
3. Hit the Filter drop-down and choose All transactions from the Type drop-down menu.
4. Click Apply. 

I've got this sample screenshot for a visual guide:

If you're still unable to see all of the transactions, you can follow the troubleshooting steps provided by my colleague IamjuViel. 

Otherwise, run the Audit log report to review if those transactions were deleted.  

Here are the steps:

1. Go to the Gear > Audit log.
2. Click the Filter drop-down list.
3. Choose the User and Date.
4. Under Events, select Show only these events and put a check mark on the Transactions box.
5. Hit Apply. 

Please see this sample screenshot:

If the transactions were deleted, there's no way to restore it. However, you can recover the details in the Audit Log, so you can re-create them. For reference, check out this link: Use the audit log to re-enter deleted transactions.

After the steps, go back to Sales > Customers > Transaction List and see if all transactions are showing up. 

You can also go to the Reports page and run the Transaction List by Customer. This will display all of your transactions (income and expenses), grouped by customer. 

I'm sharing these articles to see other reports and how to customize them:

• Reports included in your QuickBooks Online subscription
• Customize reports in QuickBooks Online

Please keep me posted on how things go after trying out the suggestions I've provided. I'm here to help you out again. Have a good day ahead!