@shuwen
It looks like you are trying to access an envelope that you do not have access to. This can happen if you are logged into Docusign eSignature with a different user than the one the envelope was intended for. If you have two Docusign accounts on different server environments, like in NA and EU, it could be caused by you being logged into the wrong data center. In this case, log out from Docusign eSignature and log back in and select the correct account that your envelope was signed in and you should have no problem to access it.