You need to write nameOfTask without "".
Also add this (so task would be marked as succeeded in briefing):
nameOfTask settaskstate "Succeeded";
Edit: You have named tasks as tskObj0,tskObj1,tskObj2 so it should look like this:
tskObj0 settaskstate "Succeeded";
nul = [objNull, ObjNull, tskObj0, "SUCCEEDED"] execVM "CA\Modules\MP\data\scriptCommands\taskHint.sqf";