Object of class stdClass could not be converted to

Hello, when I change order status to shipped I get this error

Fatal error: Uncaught Error: Object of class stdClass could not be converted to string
in /home/queenmother/public_html/wp-content/plugins/print-invoices-packing-slip-labels-for-woocommerce/includes/vendor/dompdf/dompdf/src/Dompdf.php on line 435

Call stack:

1. mb_convert_encoding()
   wp-content/plugins/print-invoices-packing-slip-labels-for-woocommerce/includes/vendor/dompdf/dompdf/src/Dompdf.php:435
2. Dompdf\Dompdf::loadHtml()
   wp-content/plugins/woo-pdf-invoice-builder/PDFGenerator.php:447
3. RednaoPDFGenerator::render()
   wp-content/plugins/woo-pdf-invoice-builder/PDFGenerator.php:419
4. RednaoPDFGenerator::Generate()
   wp-content/plugins/woo-pdf-invoice-builder/PDFGenerator.php:279
5. RednaoPDFGenerator::GenerateAttachment()
   wp-content/plugins/woo-pdf-invoice-builder/woocommerce-pdf-invoice.php:412
6. RednaoWooCommercePDFInvoice::AttachPDFEmail()
   wp-includes/class-wp-hook.php:326
7. WP_Hook::apply_filters()
   wp-includes/plugin.php:205
8. apply_filters()
   wp-content/plugins/woocommerce/includes/emails/class-wc-email.php:477
9. WC_Email::get_attachments()
   wp-content/plugins/woocommerce/includes/emails/class-wc-email-customer-completed-order.php:69
10. WC_Email_Customer_Completed_Order::trigger()
    wp-includes/class-wp-hook.php:324
11. WP_Hook::apply_filters()
    wp-includes/class-wp-hook.php:348
12. WP_Hook::do_action()
    wp-includes/plugin.php:565
13. do_action_ref_array()
    wp-content/plugins/woocommerce/includes/class-wc-emails.php:170
14. WC_Emails::send_transactional_email()
    wp-includes/class-wp-hook.php:324
15. WP_Hook::apply_filters()
    wp-includes/class-wp-hook.php:348
16. WP_Hook::do_action()
    wp-includes/plugin.php:517
17. do_action()
    wp-content/plugins/woocommerce/includes/class-wc-order.php:395
18. WC_Order::status_transition()
    wp-content/plugins/woocommerce/includes/class-wc-order.php:253
19. WC_Order::save()
    wp-content/plugins/woocommerce/includes/admin/meta-boxes/class-wc-meta-box-order-data.php:714
20. WC_Meta_Box_Order_Data::save()
    wp-includes/class-wp-hook.php:326
21. WP_Hook::apply_filters()
    wp-includes/class-wp-hook.php:348
22. WP_Hook::do_action()
    wp-includes/plugin.php:517
23. do_action()
    wp-content/plugins/woocommerce/includes/admin/class-wc-admin-meta-boxes.php:263
24. WC_Admin_Meta_Boxes::save_meta_boxes()
    wp-includes/class-wp-hook.php:326
25. WP_Hook::apply_filters()
    wp-includes/class-wp-hook.php:348
26. WP_Hook::do_action()
    wp-includes/plugin.php:517
27. do_action()
    wp-includes/post.php:4760
28. wp_insert_post()
    wp-includes/post.php:4862
29. wp_update_post()
    wp-admin/includes/post.php:453
30. edit_post()
    wp-admin/post.php:227

Can you tell me how to solve it?

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