If an ASP.NET page displays 404 status code, check Failed Request Tracing logs to see substatus code. You may see substatus code 17 with this error message: The request is not supported (0x80070032)
HttpReason: Not Found
ErrorCode: The request is not supported (0x80070032)
Solution for 404.17 The request is not supported error
This occurs when the ASP.NET handler is not installed or is not working. In this case, Static File handler runs instead and it fails because it’s a dynamic page.
You may try uninstalling and installing ASP.NET components in Server Manager but it’s unlikely to help with the issue.
Check application pool settings. In the server I troubleshot, the application pool was running with “No Managed Code” setting. After changing it to “.NET CLR Version v4.0”, the page started working.