Heroku App connected to subdomain in Netlify DNS

Hi

I have a created a small app on Heroku which is on a default Heroku domain
https://kassebil-crm.herokuapp.com/

I want this domain to be a subdomain of my main project which is hosted on my Netlify account.
Thus, my heroku app should be available at portal.kassebil.dk.

I thought it would be as easy as just creating a CNAME record in Netlify DNS at portal.kassebil.dk pointing towards the value I got from Heroku which is:

elliptical-zuchinni-p0hu5hf4xcptnkodkh8xct24.herokudns.com

However, this does not seem to work for me. What am I doing wrong here?

netlifydns

The setup seems to be correct. If you have setup everything else correctly on Heroku end, it should work. Not sure, but maybe you can try asking this to Heroku support also (if you haven’t already).