Vimium is missing the "all hosts" permission.
    
    
      Firefox requires users to manually grant this permission to extensions. You can enable it via
      the button below:
    
    
      
    
    
      Or by navigating to:
    
    
      about:addons > Vimium > Manage (click the 3 dot menu) > Permissions > 
 Enable the "Access
      your data for all websites" permission.
    
    
      See here for more info about
      this permission.
    
   
  
    
      All Vimium keys are enabled on this page.