Hi Mark Ellis, I can imagine how frustrating it must be to deal with a non-working keyboard, especially after a system update that was supposed to improve things.
To resolve the Windows 11 25H2 keyboard not started issue Code 19 disable Fast Startup by going to Settings then System and Power and Additional power settings then click Choose what the power buttons do and Change settings that are currently unavailable. uncheck Turn on fast startup and save changes or run powercfg /h off in an admin terminal followed by a full shutdown using shutdown /s /t 0. uninstall and reinstall keyboard drivers via Device Manager by expanding Keyboards right clicking the device Standard PS/2 Keyboard selecting Uninstall device and restarting the PC run the Keyboard troubleshooter from Settings then System and Troubleshoot and Other troubleshooters check for optional updates under Settings Windows Update then Advanced options and Optional updates if the issue persists use a Windows 11 bootable USB to access recovery tools and run DISM and Reagentc commands to repair system files and finally check HP’s website for BIOS or driver updates even if 25H2 specific drivers are unavailable. try installing the latest available for 23H2 as BIOS updates may improve hardware compatibility.
Have you noticed any other hardware or driver issues since the 25H2 update, or is the keyboard the only device affected?
Best regards
Lucky Charm