Posts are not showing up in my channel/collection

I am having issues creating something that would bring up all posts tagged with newsletter under my signup page so I decided to use a channel which isn’t working when I tried a collection it wouldn’t work either please help me

my routes.yaml looks like

  post: page.home
 template: page

 controller: channel
 data: page.newsletter
 filter: tag:Newsletter

template: index
permalink: /{slug}/

tag: /{slug}/

here is my newsletter page ​​ and my newsletter posts which yes are tagged with Newsletter are not populating also is there any way to add css to the post view that populates like on here

P.S if there is any other way to have all posts tagged with newsletter appear under the page I am all for it.