QB on line just sits and thinks when I try to open a new invoice. It just started doing this

I can share some troubleshooting steps to fix the issue you're having with invoices, @pulsesouthbrisba.

There's a good chance that your browser is full of cache data. Too much of it causes issues and affects the performance of your QuickBooks Online (QBO). 

To verify this, let's access your account in a private or incognito window and open a new invoice from there. This helps us narrow down the issue as this doesn't store any cache files. You can refer to these keyboard shortcut in opening a private window.

• Ctrl + Shift + N (Google Chrome browser)
• Ctrl + Shift + P (Mozilla Firefox & Microsoft Edge browsers)
• Command + Shift + N (Safari browser)

If you're able to open a new invoice, I suggest clearing your regular browser's cache to refresh the system. If this is not the case, I propose using other supported browsers. This way, we can rule out a possible browser-integrated issue. 

When everything is in place, you might want to check out this link for reference on how to modify your invoice and make your business unique: Customise invoices, quotes, and sales receipts in QuickBooks Online.

Need more help with your invoices? You can always tag me in your reply. I'll be more than happy to assist you anytime.