380sl brake change nightmare

Hey! I have recently bought a 1981 380sl and realized how bad the brakes were so I bought new ones from mercedes source (pads and rotors for the back and front) but after doing the back without a hitch really the front calipers were replaced aswell (not too big of an issue). however after this and bleeding them I am not getting brake pressure when I start my car, and my brake light is on. I suspected a master cylinder renewal might be my issue so I went ahead and got a new one and bled the system again to no avail. I get brake pressure when the car is off, and fluid flows but the brakes do not squeeze the rotors in the front but if I turn the car on I don’t even get pressure. just air through the travel of the brakes. please help asap!! I want to drive again :-(