Here are few suggestions:
1) Change the command CHECK STORY DRIFT to CHECK STORY DRIFT 1893
2) Change command DIA 11 TYPE RIG YR 33.6 33.8 JOINT XR 0 34 ZR 0 25 to command DIA 11 TYPE RIG YR 36.9 37.1 JOINT XR 0 34 ZR 0 25
With these changes I can see that summation for load cases 2 and 3 as non zero values in STAAD.Pro build 20.07.11.45.
1) Change the command CHECK STORY DRIFT to CHECK STORY DRIFT 1893
2) Change command DIA 11 TYPE RIG YR 33.6 33.8 JOINT XR 0 34 ZR 0 25 to command DIA 11 TYPE RIG YR 36.9 37.1 JOINT XR 0 34 ZR 0 25
With these changes I can see that summation for load cases 2 and 3 as non zero values in STAAD.Pro build 20.07.11.45.