Rails I18n translation missing despite being defined in en.yml

Question

I'm trying to render text in a view:

<h3><%= I18n.t('product.project_summary.exception_details') %></h3>

And my en.yml file is like this:

en:
  product:
    project_summary:
      exception_details: "Exception Details"

I checked my spaces and indentation in the en.yml file, and everything looked good. But, it still renders as translation missing: en.product.project_summary.exception_details.