Hello @Bimala Shrestha ,
welcome to this moderated Azure community forum.
So what I understand from the comments you have a web api and you receive a request coming from an EventGrid Topic destination, type Webhook?
Can you confirm that?
Did you see the 'validationUrl' in the request?
Your endpoint needs to respond on that url so you confirm you are the owner of the api.
I used a webhook in the past and my Azure Function having an EventGridTrigger takes care of this confirmation automatically.
As JananiRamesh-MSFT mentioned, it seem you use a third party service. This one-time validation call needs to be addressed.
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