One of the features of the Arcane Archer fighter subclass is Curving Shot:
At 7th level, you learn how to direct an errant arrow toward a new target. When you make an attack roll with a magic arrow and miss, you can use a bonus action to reroll the attack roll against a different target within 60 feet of the original target. [XGtE, pg. 28]
How does this interact with cover?
The PHB description of cover says, among other things:
A target can benefit from cover only when an attack or other effect originates on the opposite side of the cover. [PHB, pg. 196]
So what's the origin of a Curving Shot attack? I see two possibilities:
The origin of the redirected attack is the original, missed target.
The origin remains at the archer.