Except as otherwise provided in Section 3424, a court of this state may not modify a child custody determination made by a court of another state unless a court of this state has jurisdiction to make an initial determination under paragraph (1) or (2) of subdivision (a) of Section 3421 and either of the following determinations is made:
(a) The court of the other state determines it no longer has exclusive, continuing jurisdiction under Section 3422 or that a court of this state would be a more convenient forum under Section 3427.
(b) A court of this state or a court of the other state determines that the child, the child’s parents, and any person acting as a parent do not presently reside in the other state.