Unexpected user error. ( -10601 ) after there last update unable to send out invoices now. any one know what the problem is?

Performing troubleshooting steps can help narrow down the issue of being unable to send out invoices due to the unexpected user error, @jdland.

At times, the browser stores frequently accessed data, and unusual behaviors in any online platform, including QuickBooks Online (QBO) can cause a data issue with your browser. Let's access your account using a private browser by following the keyboard shortcut keys below: 

• Google Chrome: Ctrl + Shift + N
• Safari 11 or newer: ⌘ + Shift + N
• Mozilla Firefox: Shift + Ctrl + P
• Microsoft Edge: Ctrl + Shift + N 

If it works, send the invoice to your customer again and return to your regular browser and clear its cache to refresh the website's preferences. You can also utilize another supported browser to optimize your QuickBooks experience. 

On the other hand, if you're using the mobile app. Here's how you can perform the troubleshooting steps.

For iOS devices: 

1. Select the menu at the top right.
2. Then, choose Help & Feedback.
3. Next, click Refresh Data and select Refresh.

For Android devices: 

1. Select the menu at the top right.
2. Next, choose Settings.
3. Then, select Refresh Data and click Yes.

In case you want to personalize your sales forms before sending them to your customer, you can visit this article to learn how: Customize invoices, estimates, and sales receipts in QuickBooks Online. 

If you've got more concerns about invoices, please leave a comment below. We're always available to assist you.