Custom 'News Post' not appearing in SharePoint App

In our company portal, we release lot of news and it requires to be categorised. Hence we created a custom content type 'News Category Content Type', added a site column (of type managed metadata) and added to 'Site Pages' library. Now whenever we create a 'News Post' from the modern communication/team site and change the content type of the page from 'Site Pages' to 'News Category Content Type', it's not appearing in the SharePoint app (under NEWS tab). But if I didn't change the content type and leave it as 'Site Pages', the pages appear perfectly well in the app. The requirement of having the custom column is required to categorise and organise the news in our company. And we are building the portal so that it's mobile compatible as most of our users prefer news in the app so it's vital that the news feed we create in the site appears in the app. Kindly help!