If QuickBooks is unable to send invoices, follow these troubleshooting steps:

1. Check Internet Connection: Ensure your internet connection is stable. QuickBooks needs a reliable connection to send invoices.

2. Update QuickBooks: Make sure you’re using the latest version of QuickBooks. Updates often include fixes for known issues. Go to the Help menu, select ‘Update QuickBooks,’ and follow the prompts.

3. Verify Email Settings: Double-check your email settings in QuickBooks. Go to the Edit menu, choose ‘Preferences,’ then ‘Send Forms,’ and review the settings for your email provider. Ensure that the email service is configured correctly.

4. Review Email Templates: Sometimes, corrupted email templates can cause issues. Go to the ‘Templates’ section and try using a different template to send the invoice.

5. Check for Errors: Look for any error messages when attempting to send an invoice. Note any error codes and consult QuickBooks’ support resources for specific guidance related to those codes.

6. Repair QuickBooks: If the issue persists, consider repairing QuickBooks. Go to the Control Panel, select ‘Programs and Features,’ find QuickBooks, and choose ‘Repair.’

7. Contact Support: If none of the above solutions work, it may be time to contact QuickBooks support for further assistance. They can provide more in-depth troubleshooting and solutions specific to your version and setup.

By following these steps, you should be able to resolve the issue and successfully send invoices through QuickBooks.