Did you use new project wizard and told there you are going to use XGATE? If so, then XGATE should execute at least dummy SoftwareTrigger0_Handler() from xgate.cxgate. Doesn't it run?
If it runs, then you should do following:
1) You should either add XGSWT = 0x100; to SoftwareTrigger0_Handler(), or remove XGSWT= 0x0101; from SetupXATE() in main.c. This is to prevent software thread 0 executing again and again, taking all XGATE time.
2) add PIT handler to *.cxgate file
3) edit XGATE vectors table to point to PIT handler
4) route PIT interrupt to XGATE. Add this to SetupXGATE:
ROUTE_INTERRUPT(Vpit0, 0x81); // route PIT0 to XGATE
Now, if PIT is setup properly, XGATE shoud handle PIT interrupts