I have been using LibreOffice 5.1 daily for months.
Today it won’t launch, even immediately after rebooting my pc.
I see no error messages, no splash screen, nothing.
I also don’t see any processes added to the task manager when I double-click on any of the libre office icons.
If it was me I’d try re-installing, choose the “Repair” option, and see if that cures it.