Norton Security won't re-install

I installed Norton Security on a HP laptop I maintain for my employer. The lapttop is running Windows 10. While doing some routine updating of the laptop, I saw that Norton Security had been disabled. The folder still appeared in the Programs list, but the link to it was dead. It appears Windows Defender had re-activated, but no scans or updates had been downloaded recently. 

I tried to re-install Norton Security. The Norton Download Manager functioned as expected, but when the 'Installing" screen appears, the activity bar cycles for hours, with the installation never completing. 

The primary user of this computer has been known to indiscriminately click on links to malware/ransomware, which is why I installed what I believe to be a security package superior to Windows Defender. I suspect he has downloaded some app that disabled Norton and is harboring some as-yet-unseen and unpleasant surprise. I'd like to get Norton re-installed and run a scan on the laptop, before whatever (might be/is) on there can do some harm.