1999 Ford F 150 Had Leak Rear Brake Line Took Old One Out Installed New Section

i had a leak in the rear brake line so i took the old one out and installed a new section. when i started to bleed brakes i found that the rear bleeders would not work. through investigation we learned that the lines on the rear axle were not getting brake fluid starting where the line changes from metal to rubber. i was hoping for ideas on how to procede.