Uncaught Mpdf\MpdfException: Data has already been sent to output, unable to output PDF file
in /home/uqkawubb/public_html/wp-content/plugins/woocommerce-invoice-pro/vendor/mpdf/mpdf/src/Mpdf.php on line 9605

Call stack:

1. Mpdf\Mpdf::Output('pre-invoice(1780629161).pdf', 'D')
   wp-content/plugins/woocommerce-invoice-pro/classes/pdf-generator.php
2. WIP_PDF_Generator::download()
   wp-content/plugins/woocommerce-invoice-pro/templates/pre-invoice.php:172
3. include('/home/uqkawubb/publi...ates/pre-invoice.php')
   wp-includes/template-loader.php:132
4. require_once('/home/uqkawubb/publi.../template-loader.php')
   wp-blog-header.php:19
5. require('/home/uqkawubb/public_html/wp-blog-header.php')
   index.php:17