Deploying a custom domain with Heroku and Domain.com

I'm new to web dev and this would be my first proper deployment so apologies if this is a basic question. After following the steps on Heroku and Domain.com, my app is not showing at the desired url: www.rocketcreative.agency

Heroku I've set up a basic web app (a draft version atm) on Heroku, and the code is working fine on https://hidden-sierra-22116.herokuapp.com . I've followed the Heroku instructions to generate a DNS target (cubic-orange-7jtaz36102kt9f8dir53koko.herokudns.com) for a domain I own (www.rocketcreative.agency) Heroku Dashboard Screenshot

Domain.com I added the DNS target to Domain.com as a CNAME (with 'www' as the host name). I've waited 24 hours for the changes to propagate, and DNS checking sites indicate that the DNS has propagated. I've spoken to Domain.com support and they said everything appears to be set up correctly. Domain.com DNS Screenshot

Terminal: In the terminal, when I input host www.rocketcreative.agency, it returns www.rocketcreative.agency is an alias for encircled-horseradish-4mpqnlzar9say364tz3hgy80.herokudns.com.

Browser Results for www.rocketcreative.agency

Safari: 'Safari Can't Find The Server'

Chrome: 'www.rocketcreative.agency’s server IP address could not be found. DNS_PROBE_FINISHED_NXDOMAIN'

I imagine this is a really basic question but if anybody could help that would be great. If there's any other info I need to provide please let me know. :)