This is the last part of my YAML and I cannot for the life of me get a preview image on the home page for this post or any post.
I know there is some sort of redundancy here but I've been trying several combinations. The image does appear in the header of the post but not like the puppy image preview in the home page.

If you are attempting to use Academic v3+ then this won't work as expected as there are some old parameters present in your front matter that have not been migrated to the new version.
To migrate your front matter and configuration, apply the relevant breaking changes from the release notes. Assuming your site was previously on v2.4.0, then apply the breaking changes for the consecutive releases since v2.4.0, i.e. https://sourcethemes.com/academic/updates/v3.0.0/ and https://sourcethemes.com/academic/updates/v3.1.0/ .
Documentation for featured image and header image in v3+: https://sourcethemes.com/academic/docs/managing-content/#featured-image .
Also, the update guide has now been rewritten to make the update process clearer: https://sourcethemes.com/academic/docs/update/
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Also, the update guide has now been rewritten to make the update process clearer: https://sourcethemes.com/academic/docs/update/