Bench bleeding the master helps, but usually it's just a matter of getting air in the system.
Depending on how you're bleeding it and your whole setup, it can take quite a lot of bleeding before you get pressure on the pedal, and still even longer before you get a steady stream of air bubbles coming out and slowly less and less so you know you're doing it right.
If you learn how to do it, you can disconnect the system and not get much air in there and have less bleeding to do, but once you get air in there or have the system open, there's not really anything else you can do but bleed until you get pedal pressure back.
Make sure you're doing it right (bleeding fluid into fluid/filled container, opening bleeder screw only with fluid coming out, closing bleeder screw mid/bleed each time before air can be sucked back in, refilling fluid reservoir every bleed or every other bleed, etc.) and you should get it working eventually.