I'll ensure this is taken care of, Sonia.

First, make sure Custom transaction numbers are enabled and check the CSV file if there's an invoice number.

Here's how:

1. Go to the Gear icon.
2. Select Account and settings.
3. Click the Sales tab.
4. Tap the Sales form content edit pencil icon.
5. Turn on Custom transaction numbers.
6. Hit Save, and then Done.

Additionally, put a checkmark beside Add new customers to QuickBooks when uploading the file in case the customer you've added is not yet in the program. I've added a screenshot below for visual reference.

If everything is fine, let's perform basic troubleshooting steps. You may have accumulated too much historical data. Whenever you visit a website, it saves some information from the web page in its cache and cookies. These files allow the websites you visit most often to load faster. Not to worry, clearing them will do the trick.

First, let's try accessing your account through an incognito window to rule out the possibility of a webpage issue. You can refer to these shortcut keys to open an incognito window in all supported browsers:

• Chrome: Ctrl + Shift + N
• Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

Once done, import your invoice again. If it works, switch back to your regular browser. Then, clear its cache. This way, you can access QuickBooks with a clean slate. You can also use a different supported one.

You can also review this article to learn more about the process: Import multiple invoices at once.

I'm also adding this resource to help personalize and add specific info to your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online. This way, you'll have attractive, professional-looking customer forms.

Keep me posted if you have additional questions about uploading invoices. I'll be around to help you again. Take care!