Check out calculation of start-up cost
Check out if the following in 2c_objective.gms needs the $ts_startupCost_(unit, starttype, t) on the third line. It might not be defined for units with constant start-up costs?
//Start-up costs, initial startup free as units could have been online before model started
+ sum(uft_online(unit, f, t),
+ sum(unitStarttype(unit, starttype)$ts_startupCost_(unit, starttype, t),
+ [ // Unit startup variables
+ v_startup_LP(unit, starttype, s, f, t)${ uft_onlineLP(unit, f, t) }
+ v_startup_MIP(unit, starttype, s, f, t)${ uft_onlineMIP(unit, f, t) }
]