So after the major schoolboy error of not adding my target audience to the campaign I fixed it and wouldn’t you know it hits again!
Shock horror, advertise to the right people and bam you get a result.
However my question to anybody who has an opinion is, is it worth using the shopify channel api? After all direct through Facebook is much more flexible and the analytics are more complete.
I am going to try and run some different campaigns direct for the next couple of days and see how it goes, but I would live to hear from anybody with more experience than me (which will be the vast majority of you) if you have an opinion either way.