There's a bug that isn't automatically selecting Legendary for Glory Beyond. Your clear was on Brave. Once you complete it on Legendary and assuming you did all 5 other missions on Legendary on that character you can then speak to the bar tender in the Cantina at Tharsis Outpost. To rerun the mission on Legendary: Portal -> Renegades (top left) -> on the far left under the 'Tharsis Outpost' text you'll see a button with the Renegades icon -> click it -> click customize -> find the mission you need on the list. If it says 'activity power disabled' it's normal mode, if it says '-20 Combatant Power Delta' then its legendary.