Premailer-rails stopped working on rails version 3.2.22

I have included " gem 'premailer-rails'" in my Gemfile.

And include stylesheet like this : <%= stylesheet_link_tag "mailers/test" %> in mailer layout file, where path for css file is : app/views/layouts/test.html.erb.

For few days this configuration was working fine. But now it stopped , I an unable to figure out the reason.

My rails version is 3.2.22

Followed this link for my project : https://hackernotes.io/a-production-ready-rails-5-email-workflow-with-mailer-previews-premailer-and-activejob/

In Gemfile.lock : premailer (1.11.1) addressable css_parser (>= 1.6.0) htmlentities (>= 4.0.0) premailer-rails (1.10.3) actionmailer (>= 3) premailer (~> 1.7, >= 1.7.9)

Any leads will be very helpful.