DNS setup for double subdomains with Advanced Certificates

I have an app hosted on netlify: myapp-staging.netlify.app
I have a domain: mydomain-staging.com
I setup a cname: myapp - myapp-staging.netlify.app
I added a origin server certificate to netlify for mydomain-staging.com *.mydomain-staging.com

https://myapp.mydomain-staging.com is served properly.

Now I want to have additional subdomains to make this possible:

I purchased Advanced Certificates and added a new certificate for:
*.myapp.mydomain-staging.com *.mydomain-staging.com mydomain-staging.com

I deleted the old origin server certificate and created a new one for *.myapp.mydomain-staging.com mydomain-staging.com *.mydomain-staging.com
I updated the netlify custom certificate with this new origin server certificate.

I added a cname: project-a.myapp - myapp-staging.netlify.app

https://myapp.mydomain-staging.com is still served properly.

https://project-a.myapp.mydomain-staging.com results in: Not Found - Request ID: <some-id>

How do I set this up properly?

I managed to solve this. I needed to add a domain alias in netlify for project-a.myapp.mydomain-staging.com