What firmware are you running? (System Settings>System Information)
Firmware 1.00 and 1.50 are they only firmware that can run homebrew from the menu. 1.5 can be downgraded to 1.00 but there isnt much point as all homebrew runs flawlessy on 1.5.
Firmware 2.00, 2.01, 2.5 and 2.6 all need an unpatched version of GTALCS and the eloader installed. The eloader can only run limited homebrew. 2.00 can be downgraded to 1.5 using the MPH downgrader. 2.5 and 2.6 can be downgrader to 1.5 using the DOWNDATER.
Firmware 2.7 and 2.71 can't run any homebrew nor can it be downgraded.