Complex sentence: After several more attempts at French conciliation failed, in September 1664 Marguerite Louise left her apartment in Palazzo Pitti, refusing to return; therefore, Cosimo moved her into Villa di Lappeggi.
Split into simpler sentences: After several more French attempts at conciliation had failed, in September 1664 Marguerite Louise left her apartment in Palazzo Pitti, refusing to return. As a result, Cosimo moved her into Villa di Lappeggi.