Questions

The Agreement   on   Trade-Related Aspects   of   Intellectual   Property Rights(TRIPS)   is   an international legal   agreement between   all   the member    nations    of    the World Trade  Organization(WTO).  It  sets down  minimum  standards  for  the regulation by national governments of    many    forms    of intellectual property(IP) as applied to nationals  of  other  WTO  member nations.TRIPS  was  negotiated  at the  end  of  the  Uruguay  Round  of the General  Agreement  on  Tariffs and  Trade  (GATT)  in  1994  and  is administered by the WTO

The error is in second part. In the given sentence two events occur one after the other. ‘He left’ before ‘we reached’. So, the event that was completed before the occurrence of the next event shall be expressed in past perfect tense. Therefore, the correct form of verb will be “had left”.