The issue is similar to the issue described in the this question but the mitigation steps did not help.
In the Azure portal I have tried to create an app managed certificate for my-react-app.mydomain-qa.com domain and got the following error:
Properties.CanonicalName is invalid. Canonical name my-react-app.mydomain-qa.com is not a subdomain. This validation method only supports subdomains.
It states that the name is not a subdomain which is wrong. I have the following DNS records:
CAA @ digicert.com 0 issue
CNAME my-react-app my-react-app.azurewebsites.net
I have also tried to use the script which gave me the following error
Properties.CanonicalName is invalid. Not found A record directly pointing to outbound ip address of website my-app-service-name. Current A record record of the hostname is empty.
Which tells me that the domain is not an apex domain which is correct. I could not find any documentation about the domainValidationMethod parameter in order to make it treat the name as subdomain.