5d mark III compact flash problem

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After installing magic lantern my compact flash slot does not work. I have tried multiple compact flash cards, and the camera fails to boot, or have any indication of function. But SD cards work normally. I have removed the battery, switched the lens, tried different firmwares, and done everything I can think of. I just want the speed of the compact flash card back. Please help. Sorry for my poor English, it is not my first language.