If anyone has had a black screen after attempting to install Cumulative Update KB 4103721, and has Advanced System Care 11 installed, here is the fix:
Rebooting to Safe Mode will trigger a rollback of the update, but you’ll need to reboot to Safe Mode a second time to finish the rollback and perhaps a third to actually get into Safe Mode. Once there, you can reboot into Windows.
In Services, shut down and disable Advanced SystemCare Service 11, reboot and then install the update. Once installed you can enable and start the service again.
