I have looked around the forums but failed to find a solution to my problem. I have installed the global site tag and event snippet as shown in the shopify tutorial. I pasted the event snippet into the additional scripts part of the checkout and the global site tag in the theme.liquid as seen in the images below.
When checking the source code or using google tag assistant the tags can be found on all pages except the checkout and thank you pages, see the source code for thank you page below.
I am really not sure what I have done wrong here, so any help would be very appreciated. Thanks for your time
It seems that those pages use a different layout. What you have in theme.liquid doesn't match with the thank you page source code.