Thanks very much for getting in touch to try help me with this issue!
I did have it in my functions.php initially as I wanted it to work across a couple of post names such as Wedding , Ceilidh , DJ etc but I did move it into the archive page and singular pages to see if it made a difference which unfortunately had no joy
I put the code that you suggested and tried moving it around the templates and functions and it still has not worked
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