I'm not completely sure but I think that this happens because your OnMinute36 label is not calling anything in the bidder to start its timer.
I've not tested in-game, but maybe this will fix the problem:
At the end of OnMinute36: (add the donpcevent)
announce "The portal has been closed.",0;disablenpc "Pracewarp";donpcevent "Bidder#prace0::OnStart1";sleep 5000;
In the bidder, change Start1: to OnStart1: and at OnTimer120000: change goto Start1 to goto OnStart1
Hope it helps.