Got 'Power Plant' but Rex still unplayable?

[Nephi]

I brought the Fuel Array to Rex in the Abyssal Depths and got the Power Plant achievement. I then quit to main menu as it was a terrible run and it'd take longer to find something to die to.

Rex is still not in the list of selectable survivors. The achievement is still unlocked in the Logbook.

Am I supposed to do something else? All the unlock guides stop after that achievement.

[Abyssheart]

The only thing I can think of is do the Quest again and this time die or end the game via portal.

[Fangsgalaxy5]

When you quit the game you don't get the items you unlocked. You have to die in order to get the items or progress you made.

[Xilo The Odd]

dying isnt too hard in abyssal, simply start the portal event, and force yourself to take as much fall damage as possible.

[Buffmania]

There's been some reports that some older mods prevent Rex from showing up in the roster select even after being unlocked.