Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
Hello @Admin
Thank you for confirming that the issue is resolved. As mentioned, when checked in backend certificate is bind to the domain. As suggested by community member @TP may be the issue could be with registering the domain.
Please feel free to reach out to us in case of any queries. We're happy to help you.
Providing the Microsoft documentation for setting up custom domain to app service.
https://docs.azure.cn/en-us/app-service/app-service-web-tutorial-custom-domain?tabs=root%2Cazurecli