Not able to complete order Shopify HPSDK

[Akshay3]

I have created my own Shopify payment gateway, I am trying to mark order as completed on my test store using HPSDK method but getting following error.

I am also trying to make asynchronous callback which is also giving me an error "Notification acknowledgment failed".

Can anyone give me idea what I am doing wrong here? 

[CalD]

Hey @Akshay3,

Have you confirmed the signature you're gateway is calculating is correct? https://shopify.dev/docs/hosted-payment-sdk/getting-started#422-unprocessable-entity-notification-ac...

Can you also rule out this similar-sounding issue? https://community.shopify.com/c/Shopify-APIs-SDKs/refund-order-management-response/td-p/513532 

If necessary after checking the above items, send over an x-request-id response header from one of your unsuccessful callback requests and we can look at the logs further.