Exact issue has been discussed here:
https://discourse.gohugo.io/t/render-hooks-not-hooking/23605/8
{{ $c := .Content }}
{{ .copy | $.Page.RenderString }}
Unfortunately this approach of making sure .Content is present on the page doesn’t work for me.
When I download ghandiShepard’s repo I can see the fix working so I will now need to figure out why it works on that site and not mine.
Edit: If I build a quick shell of a new site this works for me but I have no idea why its not working in my current project.