I have over 1500 invoices for one customer, but search only shoing 500???? It happened first time?????

I can help you look for these missing invoices, @sal5.

Try to use the Advanced Search feature in QuickBooks Online (QBO) to look for these invoices.  You can go to the magnifying glass icon to look for these invoices.

Here's how:

1. Click the Magnifying Glass icon and select the Advanced Search.
2. Adjust the filters to Invoices, Customer then the specific customer. 
3. Also, don't forget to set the date filter that'll greatly affect the number of invoices that you can search.
4. Click on the Search button.                 

You can go to the following article for more information: Search for transactions.

I'm always here to help you find those invoices. Let me know in the Reply section below. Take care and have a wonderful day!