Could you hit the Rescan Asset button on the computer's Lansweeper webpage, wait for the scan to complete and see if the install date shows up in the computer's Software tab. If it doesn't, the install date isn't stored in the client machine's registry, which is something we can't fix.
Lansweeper pulls software install dates from the client machine's registry. It is known that not all install dates listed in Add/Remove Programs on a Windows computer are stored in the computer's registry, which is why Lansweeper is unable to retrieve all of them.
This online topic explains how Windows retrieves the install dates listed in Add/Remove Programs. Some are stored in the registry, some come from a WMI class and some are the last modified date of the software's uninstall key in the registry. Our developers deliberately programmed Lansweeper to only pull install dates directly stored in the registry, as the other dates listed in Add/Remove Programs tend to be wildly inaccurate. Install dates based on modification dates of uninstall keys are not accurate for instance, because they'll change every time the software package is updated or changed in some way.