IPv6-only Update Error 502

I was using Windows Powershell + .ps1 script + Invoke-WebRequest(curl) + ScheduledTask to update my ipv6 address, but one day I found that my host was no longer accessible, and the last update was two months ago.
Here is the powershell output:

PS C:\Users\Pil0tXia> d:\[Work]\Web\DDNS\IPv6\dynv6\updateip.ps1
curl : 远程服务器返回错误: (502) 错误的网关。
所在位置 d:\[Work]\Web\DDNS\IPv6\dynv6\updateip.ps1:1 字符: 1
+ curl "http://ipv6.dynv6.com/api/update?ipv6=auto&token=b_Ec2rpi5qUR4J ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest],WebException
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

It shows a HTTP 502 Error.
Then I went to test-ipv6.com to examine my network, it works fine.
I tried dynephant to update, and it doesn’t work. Its log files are of low reference value.
But my meibu.com ipv6 ddns client works well.
What should I do? Thanks!