When you add Standard SKU Web App endpoints to Azure Traffic Manager and encounter a degraded state, there could be a few potential causes for the issue:
Health checks: Azure Traffic Manager periodically performs health checks on the endpoints to determine their availability. If the health checks fail consistently, Traffic Manager may mark the endpoints as degraded. Ensure that the health checks are properly configured and that the Web Apps are responding correctly to the health probes.
Endpoint configuration: Verify that the endpoints in Azure Traffic Manager are correctly configured. Ensure that the endpoint types, addresses, and ports match the settings of your Web Apps. Double-check the configuration to ensure there are no typos or mistakes.
DNS propagation: After adding the endpoints to Azure Traffic Manager, DNS propagation can take some time to propagate across the internet. It's possible that the 404 error you're experiencing is due to the DNS not fully propagating. Give it some time and try accessing the Traffic Manager DNS name again after a while.
Endpoint health: Ensure that your Web Apps are in a healthy state and can handle incoming requests. If there are any issues with your Web Apps, such as configuration errors or resource limitations, it could lead to a degraded state in Traffic Manager.
To troubleshoot the issue further, you can check the Traffic Manager monitoring logs, review the health probe results, and inspect the logs and diagnostics of your Web Apps for any error messages or issues.