Instagram API问题“我一直得到”无效的响应“虽然我正确回应他们正在发送的字符串”

So I have an issue with Instagram API real-time updates. I can't seem to be able to register a tag on my website. I keep getting this error

object(stdClass)#267 (1) { ["meta"]=> object(stdClass)#268 (3) { ["error_type"]=> string(20) "APISubscriptionError" ["code"]=> int(400) ["error_message"]=> string(16) "Invalid response" } }

After reading a whole bunch a lot of people wrote that perhaps its that I am not echoing the hub_challenge. Which I am and I am even saving it on a database to make sure the string is been echo.

I have even done www.xxxxx.com/callback?hub_challenge=xxxx; to make sure that the hub_challenge get request is working. Everything seems fine but I can't, for the life of me, register a tag can someone please help me!