Caps Lock button's green light not working after Mojave update
Solution 1:
I would suggest your reset your NVRAM, following the procedure from Apple.
https://support.apple.com/en-us/HT204063
Solution 2:
If you are running Karabiner that could be the issue. Try updating Karabiner and this should solve your problem. Should that not help, check your version of Office...sounds crazy but when I updated from 2016 to 2019 quite a few bugs 'magically' disappeared.