Help conjugating

"Never managed to do it again" implies some sort of "doneness," i.e. one has given up trying to do it again. This tense is called the preterite. The focus is on the action (in this case, the failure to make fire again).

"Have never managed to do it again" implies some sort of continuity, i.e. one is still trying. This tense is called the present perfect. The focus is on the consequences of the action (in this case, drawing attention to the potential consequences of having failed to make fire again), or the duration of the action (in this case, the fact that the person has tried to make fire multiple times, always failing, and may still be trying).

Both are correct, they just mean different things.