Magento 1.9.3.
Installed https://marketplace.magento.com/chapagain-chapagain-googletagmanager.html and it is working properly when viewed source code the GTM tag starts and ends immediately after tag opens.
I have added Facebook Custom Chat Plugin code as advised https://www.simoahava.com/analytics/add-facebook-messenger-chat-google-tag-manager/ but the chat window still won't show on my website.
