A cloud-based identity and access management service for securing user authentication and resource access
Thank you for posting your query on Microsoft Q&A, from above description I could understand that you are looking to get an SSL for your domain to enable HTTPS for an Azure App service.
Please do let me know if this is not the case by responding in the comments section.
The custom domain could be validated by using a txt record.
Make sure you can edit the DNS records for your custom domain. To edit DNS records, you need access to the DNS registry for your domain provider, such as GoDaddy. For example, to add DNS entries for contoso.com and www.contoso.com, you must be able to configure the DNS settings for the contoso.com root domain. Your custom domains must be in a public DNS zone; private DNS zones are not supported.
As per Map an existing custom DNS name to Azure App Service you need to:
Once done your custom domain should be verified to be used with app services.
If above does not help then please do share the screenshot of the error and details of the repro steps you have been performing.
Thanks,
Akshay Kaushik
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