To resolve this problem, upgrade to Pulse Desktop Client 9.1.9.4983 and above. If upgrade is not possible, please refer to the workaround section below:
Workaround 1:
- Double-click on the PKG file
- Click OK
- Navigate to Security & Privacy > General
- Click Open Anyways
- Click Open
Workaround 2:
- Right click on the downloaded PKG file
- Click Open With > Installer (default)
- Click Open