Title: Causing “Internal Error” message on checkout
Last modified: January 30, 2018

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# Causing “Internal Error” message on checkout

 *  [ltudbd](https://wordpress.org/support/users/ltudbd/)
 * (@ltudbd)
 * [8 years, 8 months ago](https://wordpress.org/support/topic/causing-internal-error-message-on-checkout/)
 * Hello,
    It appears this plugin is causing a “Internal Error” message to be displayed
   after an order is submitted on checkout. WordPress version “4.9.2” and WooCommerce
   version “3.3.0”. Checked our logs and got “2018-01-30T12:42:50+00:00 CRITICAL
   Call to a member function get_pdf() on null”. I deactivated the plugin, all works
   well. This error is causing customers to do the order again thinking the first
   order did not go through resulting in duplicate orders. This error is gone since
   I deactivated the plugin. Any idea on what is happening?
 * I use this plugin to auto print packing slips with the WooCommerce Print Orders/
   Google Cloud print
    Thank you

Viewing 3 replies - 1 through 3 (of 3 total)

 *  Plugin Contributor [Ewout](https://wordpress.org/support/users/pomegranate/)
 * (@pomegranate)
 * [8 years, 8 months ago](https://wordpress.org/support/topic/causing-internal-error-message-on-checkout/#post-9921404)
 * Hi! I’m sorry to hear that. To determine what causes this, I need a bit more 
   information. First and foremost, which version of “WooCommerce Print Orders” 
   are you using? (latest is 2.7.7).
    What’s the full error after the “function 
   get_pdf() on null” bit? This helps in determining where this is triggered exactly.
   If you have a stack trace, even better. Which version of PDF Invoices are you
   using and did you recently update from a 1.X version (or have you been using 
   2.X for some time already?).
 * Let me know and I’ll do my best to help!
    Ewout
 *  Thread Starter [ltudbd](https://wordpress.org/support/users/ltudbd/)
 * (@ltudbd)
 * [8 years, 8 months ago](https://wordpress.org/support/topic/causing-internal-error-message-on-checkout/#post-9923008)
 * Hello,
    Thank you for your reply. We have the WooCommerce PDF Invoices & Packing
   Slips version 2.1.4. This shows as the latest version here: [https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/](https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/)
   so we were unaware there was a newer version. How do we get the latest version?
   Also, the version of “WooCommerce Print Orders” by: [https://www.simbahosting.co.uk/s3/product/woocommerce-automatic-order-printing/](https://www.simbahosting.co.uk/s3/product/woocommerce-automatic-order-printing/)
   is “Version 2.5.1”. Everything worked up until we updated WordPress to the latest
   4.9.2 and WooCommerce to 3.3.0. The last three errors we got were: 2018-01-30T12:
   12:28+00:00 CRITICAL Call to a member function get_pdf() on null
 * 2018-01-30T12:14:55+00:00 CRITICAL Call to a member function get_pdf() on null
 * 2018-01-30T12:42:50+00:00 CRITICAL Call to a member function get_pdf() on null
   
   we then deactivated the WooCommerce PDF Invoices & Packing Slips plugin and the“
   Internal Error” message is gone and all orders are being processed as expected
   without issue.
 * Thank you!
 *  Plugin Contributor [Ewout](https://wordpress.org/support/users/pomegranate/)
 * (@pomegranate)
 * [8 years, 8 months ago](https://wordpress.org/support/topic/causing-internal-error-message-on-checkout/#post-9925238)
 * Hi!
    I think you found the issue: WooCommerce Print Orders is heavily outdated
   at 2.5.1, as mentioned in my post 2.7.7 is the latest (indeed you’re already 
   using the latest of PDF invoices at 2.1.4). 2.5.1 is not compatible with WooCommerce
   3.X (required Print Orders 2.5.5 minimum) and also not compatible with PDF invoices
   2.X (requires 2.5.17 minimum)
 * I recommend checking if your license for print orders is still valid and contact
   Simba Hosting support about getting the latest version.
 * Ewout

Viewing 3 replies - 1 through 3 (of 3 total)

 The topic ‘Causing “Internal Error” message on checkout’ is closed to new replies.

 * ![](https://ps.w.org/woocommerce-pdf-invoices-packing-slips/assets/icon-256x256.
   png?rev=2189942)
 * [PDF Invoices & Packing Slips for WooCommerce](https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/woocommerce-pdf-invoices-packing-slips/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/woocommerce-pdf-invoices-packing-slips/)
 * [Active Topics](https://wordpress.org/support/plugin/woocommerce-pdf-invoices-packing-slips/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/woocommerce-pdf-invoices-packing-slips/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/woocommerce-pdf-invoices-packing-slips/reviews/)

 * 3 replies
 * 2 participants
 * Last reply from: [Ewout](https://wordpress.org/support/users/pomegranate/)
 * Last activity: [8 years, 8 months ago](https://wordpress.org/support/topic/causing-internal-error-message-on-checkout/#post-9925238)
 * Status: not resolved