Make sure you have some DKP systems initialized. Head to Admin, and under "DKP Systems" there should be a named DKP system and links to "Decay" and "Edit." If there aren't, then click "Create a DKP System" and make a new one. That will initialize the system.
I have a DKP system set up already called General that was initialized previously, but it looks like when I hid the menus from the Basic Menu Administration page, it checked off the Hide DKP Sytem from the DKP System Administration menu. All better now, thanks for the tip