If you are making an attack and you roll a natural 1 on the die, you immediately know this is a failure. But the Lucky feat (PHB, p. 167) says:
Whenever you make an attack roll, an ability check, or a saving throw, you can spend one luck point to roll an additional d20. You can choose to spend one of your luck points after you roll the die, but before the outcome is determined. You choose which of the d20s is used for the attack roll, ability check, or saving throw.
Since an attack roll of a natural 1 is an automatic miss and is immediately known (or determined), does this allow or prohibit the use of the Lucky feat to reroll the attack?