Emoji shortcut no longer works on Macbook Air

I've see a few posts about this from 2021, but no solutions. Since I bought this Macbook Air a few months ago I've been using 'Command+Control+Space' to open the emojis window. This has suddenly stopped working - it seems to be since I installed the recent security update. I tried System Preferences; Keyboard & checking the 'show input menu in menu bar' - a small icon appears in the top menu bar, but when I click 'show emojis and symbols' it only works occasionally. Is this a known issue, and is there any solution? Thanks