Imported Posts Not Publishing

I’ve imported around 300 posts to a new version of WordPress on a subdomain. I manually imported through the admin area and the posts, authors, categories etc. all transferred over.

The posts show on the homepage along with excerpts underneath them but when you click on the title it goes to a 404. It happens with categories as well.

I’ve recreated the permalink structure as well as the authors etc. What could be keeping WordPress from fully publishing these posts?