Upgrading to WEBppliance Pro 3.5.16 fails with an error:
Action Result Status
Result Status failed
Short Description Running pre_install pro-lh-unlimited-3.5.16-2.svc failed with 1. 
A license suite already seems to be installed on this server. Please uninstall the old license suite before applying a new one.
You cannot upgrade the 3.5.10 WEBppliance Pro License Pack suite to the 3.5.16. There is no difference between the two suites so you do not need to upgrade this suite. When upgrading WEBppliance, do not select the newer license pack suite if a license pack is already installed. After the upgrade is complete and if you want the 3.5.16 license pack suite installed then uninstall the old version and re-install the new license pack suite.