When installing or upgrading the Pulse Secure Desktop Client on Windows the installation fails and the following error message is displayed:
Error 1721. There is a problem with this Windows Installer package. A program required for this install
to complete could not be run. Contact your support personnel or package vendor.
Screenshot of error:

The error will be recorded in the Windows MSI log as follows:
MSI (s) (0C:28) [09:49:47:088]: Product: Pulse Secure -- Error 1721. There is a problem with this Windows
Installer package. A program required for this install to complete could not be run.
Contact your support personnel or package vendor. Action: exe_imm_StopJuniperPulseTray,
location: C:\Program Files (x86)\Common Files\Juniper Networks\JamUI\,
command: "C:\Program Files (x86)\Common Files\Juniper Networks\JamUI\pulse.exe" -stop
To run the installer and obtain the MSI Verbose Log, execute the following command from the command prompt.
msiexec /i C:\<path to Pulse msi> /l*v C:\Logfile
Pulse versions affected:
This issue can occur when upgrading to a version of Pulse client with rebranded file directories for "Pulse Secure" where an older version has been installed on the client PC that used the "Juniper Networks" directories.