If your new keyboard is a USB keyboard, un-plug it and start the computer with no keyboard. If it starts up, then plug in the USB keyboard. The BIOS may have a setting to use a USB keyboard/mouse.
If it is a PS2 keyboard, try out the keyboard by accessing the BIOS. See if it can navigate to various setting pages. If successful, check settings to see if a PS2 keyboard needs to be selected as they type to be used. If there is another computer, try it there. Verify it works.