In the original timeline, after reverse flash did his killing business he was stuck in the past. He develops his 20 year master plan to return to his future, impersonating some one and manipulating events 20 years long in his favor.
After restoring the timeline (undoing flashpoint) together with Barry, if I remember right, it looks as if Barry was exhausted and reverse flash returned him back to his present in front of his house and after that, leaves. If this is true, then he didn't get stuck 20 years ago in the past and the timeline should have changed again dramatically. The main villian of season 1 would not be there. And we know from dialogs later in season 3 that he still was.
So what happened to reverse flash after he brought Barry back to his present? How managed he to get stuck 20 years in the past reserving the timeline? Or did he voluntary go back 20 years again, exhausting his energy to preserve the timeline instead of just returning home (or try to start from the present instead of 20 years ago)?