Please see the attached Staad model and Problem 7-001.pdf from Sap2000 verification example.
The Sap2000 results are very close to those in the literature: Peyrot, A.H., and A.M. Goulois. 1979. "Analysis of Cable Structures". Computers and Structures, Vol. 10. pp. 805-813
The Staad pro results for 5 slanted cables are close to those in the Sap2000 verification example;
but the result of the vertical cable is different from that in the Sap2000 verification example.
Is there any reason for this issue?