If your MacBook won’t power on when the BMS cable is connected, it’s likely a hardware issue rather than security settings, most often a bad BMS board, faulty cable, or improper connection after the iFixit battery install. Try reseating the cable carefully, inspect for pin damage, and test with the BMS if possible to isolate the fault. If it still refuses to boot, the logic board may be rejecting the BMS signal or there’s a short somewhere, so you might need a professional repair cause it can get tricky fast.
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