Short tags in emails not working

Hi and thank you for an awesome plugin. Guaranteed I’ll become a paying customer in the not too distant future.

For now, I am using HTML version for the site emails but the info that should appear in the emails generated by the short tags isn’t working. For example, in the backend, the “pending review” email has the content,

Hi {display_name},

Thank you for signing up with {site_name}! Your account is currently being reviewed by a member of our team.

Please allow us some time to process your request.

This is what arrives in the inbox.

Thank you for signing up!
Your account has to be manually reviewed.
Please allow us some time to process your request and review your information.

The wording is different and more importantly no display_name or site_name.

Thoughts?

https://www.ads-software.com/plugins/ultimate-member/