You may observe PECTagent closes the process really fast inside WinPE.
Looking at logs you will observe that after "Initial Deployment: Requsting InitialDeployment.aspx, request"
There is a error message:
Running: GeneralException occured 'Authentication failed, server refused to authenticate with the provided credentials or the user account is locked', return code 3, location 'WebUtil.cpp:772'
DS 8.7.1
Either account used is locked or some IIS security settings are off.