I changed the keyboard

if rebooting it doesn't fix it, you might need to go on the manufactures site,ie:hp.com, and click on support, have your serial number ready and model number, go to drivers and software downloads, on the search bar, type in your model number and it should list all the drivers that your system requires. download them and follow the on screen instructions, you might have to unzip the files. then restart your system and it should be good to go if the keyborad is a good one.

hope this helps, if not, take it to abest buy and ask them for advise, they usualy tell you how to fix it if it is an easy fix.

good luck