how to debug a controller not being run my code below results in a page not found when I browse to the path.  How can I debug what is going wrong? I dont see any errors and I have cleared the cache.

mymodule.content:
  path: '/admin/viewfiles'
  defaults:
    _controller: '\Drupal\mymodule\Controller\FileView::content'
    _title: 'File Operations Module Description'
  requirements:
    _permission: 'access administration pages'
thanks i had a misspelling in the router name. thank you all