@AnaghaPingale
You can only access the envelopes via API that were sent from your DocuSign account. With Admin permissions you can search all envelopes regardless of who the sender for the specific envelope was or you can use the user as a filter to only find the envelopes for a specific user.
Envelopes send from other DocuSign accounts to users in your account to sign or for a different action cannot be retrieved via the API as your DocuSign account is not the owner of the envelope.
You can use this endpoint to list all envelopes for a user by providing email and user_name.