One of the reason for this can be Anti-Virus installed on customer's machine. If that AV is not white-listed then I blocks Cloud's app. Please follow these steps-

  1. Go to AV and disable it temporarily 
  2. Run Connect file again
  3. Note down AV name and version
  4. Share it with us at with session id
  5. We'll whitelist that AV for to avoid such issues in future