Hot keys Shift+Ctrl+End and Shift+Ctrl+Home stopped working

I started experiencing the same problem and narrowed it down to the "Opera" browser (version:63.0.3368.88, latest at the moment of writing). Closing Opera restored Shift+Ctrl+End or Shift+Ctrl+Home behavior for me.

UPDATE: I've found the related topic on Opera forums: https://forums.opera.com/topic/35038/latest-opera-update-breaks-essential-ctrl-shift-home-end-windows-shortcuts

Some program might have taken over these shortcuts.

Try to boot in Safe Mode and check if this is still happening, then reboot in normal mode.

If it is still happening, then Windows is corrupted. Try to check its integrity using SFC and DISM.

If it is not happening any more, then some installed program is sabotaging these hotkeys. Download and install Autoruns and run it to see all startup programs. You can here disable and enable programs by their check-mark. If you cannot guess which one is it, you will need to do the hard way by unchecking them in bunches and rebooting. Re-enable those that cause no problem.

To put Bruno's comment into a proper answer, this is how you fix it, taken from the Opera forums:

https://forums.opera.com/topic/34954/opera-shortcut-key-delete-history/5

Close Opera, then navigate to Opera's folder inside your appdata folder. It may look something like:

C:\Users\USERNAME\AppData\Roaming\Opera Software\Opera Stable

Inside that folder is a Preferences file (no file extension). Open it and delete the Control-Shift-End and Control-Shift-Home keys in the JSON. For me, in Notepad, it looks like:

Delete that, then you can use Opera again without it breaking the Windows key combinations.