Normally integrating the preview feature is strait forward with Nuxt.js if you are using the @nuxt/prismic module, but this might depend on the platform you are using to deploy your application.
And in order to troubleshoot this issue, I would need more info such as the platform your using and some code sneppit of your Preview implementation.
Also have you tried to test the previews locally, and can you link to the similar thread you have mentioned?