Using the following

def op_logo_thumb_url 
  Rails.application.routes.url_helpers.rails_blob_url(op_logo.variant(:thumb))
end

Initially, i was getting errors

LoadError (Could not open library 'vips.42': dlopen(vips.42, 0x0005): tried: 'vips.42' (no such file)

So Installed the missing dependency

brew install vips

All working now.

Thank you