DIAGNOSIS A failed or interrupted firmware update can leave the system in a partially updated, unstable state. This causes odd behavior like random reboots, settings not saving, or features disappearing.
FIX You need to manually re-flash the firmware. First, go to Netgear's support site and download the latest firmware file for the RBKE963 router. Log into the router's web interface (orbilogin.com). Go to Advanced > Administration > Firmware Update. Click "Manual Update" and browse to the .img file you downloaded. Do NOT unplug anything during this process. Let it complete and reboot on its own—it will take several minutes. The ring light will pulse white and may reboot a couple times.
IF THAT DIDN'T WORK If you can't access the web interface at all, you may need to use the Netgear Nighthawk app for a recovery update, or perform a factory reset (see the other question) and then try updating again on a fresh system.
HEADS UP Always update firmware from a computer connected via Ethernet cable to the router if possible. It's more stable than WiFi. Also, don't update during peak internet usage times in your house. Let it run when no one is streaming or gaming.