silverlight will not install with safari 12.0, many applications use this Microsoft extension.
Suggestions besides reinstall IOS. Trying to reinstall Safari 11.1.2 but seem to get blocked or won't install.
No ad pop up blockers. Help
MacBook Pro (Retina, 13-inch,Early 2015), macOS High Sierra (10.13.6)
Safari dropped support for most plugins and Silverlight is one of the plugins that isn't supported.
If you have a backup, you can restore your computer to a backup made prior to installing Safari 12. Individual applications included as part of the OS can't be restored.
If you are running 10.13.6, boot into the Recovery Partition and reinstall the OS to get Safari 11.
silverlight will not install with safari 12.0
