@Martin Brugger Thanks for asking question! Could you please Go to Azure portal, open your App and check from diagnose and solve for managed certificate to see error details-
Also, please make sure that the A record of the domain is mapped properly to the IP address of the web app. Also, make sure your web app is accessible from the public network and does not have any IP restrictions set up.
The free ASMC has some limitations, please take a look. Reference doc.
The free App Service Managed Certificate (ASMC) comes with the following limitations, kindly review or validate for your domain:
• Does not support wildcard certificates.
• Does not support usage as a client certificate by using certificate thumbprint.
• Does not support private DNS.
• Only supports alphanumeric characters, dashes (-), and periods (.).
Free certificates are issued by DigiCert. For some domains, you must explicitly allow DigiCert as a certificate issuer by creating a CAA domain record with the value: 0 issue digicert.com
.
If the issue persists, suggest you create raise support ticket. Please let us know if issue remains, happy to assist.