in automated messages, {subscribe.url} remains unsubstituted

We are sending a confirmation email to a new contact. In the email, we reference

{subscribe.url} and {subscribe.group} is correctly substituted, but {subscribe.url}

is not:

mailing body message component:
Please confirm your email address with the following link:

{subscribe.url}

Didn't expect this email? Please disregard with our apologies.

Our reference: {subscribe.group}


resulting email:
Please confirm your email address with the following link:{subscribe.url}

Didn't expect this email? Please disregard with our apologies.

Our reference: Stand up for your freedom to install free software