"Don't Fear the Reaper" gone wrong.
Set-up: Harry died multiple times in multiple different ways, over and over, until the final time he even was sent back with his memories from the life before the final one.
He failed again.
Now that Harry is gone. His soul wiped and recycled with a black mark- forever barred from any life where the soul will matter or have any impact on the world. Destined to never again have any role of importance.
That still leaves the Prophecy needing to be fulfilled and Voldemort stopped. So its time for a new soul to take on the job/role.
SI/new soul gets sent back (at any point of choice, from pre-first year, to any point later in the timeline, and not limited to canon- see below)
The new soul, not being familiar with magic, is sent back with the combination of all the memories of each of the previous lifetimes/timelines. None of them canon.
I'll repeat that: none of the previous lifetimes were Canon.
Some were in each of the different Hogwarts Houses, some had him leaving the country/trying to run from his destiny, some had him getting raised outside the country only to be found and dragged back away from the ones who raised him, some had things go horribly wrong (arrive to warn Hermione only to find the troll dragging her dead and broken body, getting knocked off his broom by Quirrel, surviving when the scarcrux got taken and medical aid was able to "revive" him, Ron refusing to go get treated for the dragon bite only to end up dying from the venom, only for him to then end up dying to the Devil's Snare), etc etc.
So the new soul/"Harry" has to figure out what to do when none of the memories of the past lives actually resembled Canon, and even the closest examples just showed him not having/being able to rely on luck/plot armor.