The master cylinder has two outputs - one for LF & RR; one or RF & LR. That is the usual fail-safe so that if one line is cut, you still have some braking.
That mixed with the ALB system presents all sorts of "opportunities".
The bleeding sequence, per the manual, is RR, LF, LR, RF.
Besides the questions from EdinKali, make sure the fluid level is adequate in the master cyclinder. If its low, its possible to get air in just one of the outputs.
It sounds like one of the outputs is bad in your case. If neither RF or LR will "bleed", some possibilities are:
Low brake fluid
One bad output section of master cylinder
Blocked brakeline from that seciton of master cylinder
Anti-lock brakes have shut off RF & LR (unlikely)
I'd start by loosening the output fitting about one turn (+/-) of each line from the master cyclinder, one at a time, push on the brake pedal, and see if any fluid comes out. If fluid only comes out on one of the lines, you have found the bad section of the master cyclinder.