Are you using the v.12 or v.13 version of plugin Google Tag Manager for WordPress?
I have noticed the same issue as well on the website I manage. I can track anything (from the Product View to the Cart steps and Checkout final steps) except the orderCompleted step! It was perfectly working until the 24th of May.
Is there any alteration in this datalayer gtm4wp.orderCompletedEEC within the latest version of plugin Google Tag Manager (v.13) ? It seems like it doesn’t trigger anymore, therefore no ecommerce data is sent to Google Analytics.
Thank you so much,
Sabina