I have upgraded our ServiceDesk from 8000 to 8027 without any issues but when I take the next step to 8100 ManageEngine_ServiceDesk_Plus_8_1_0_SP-0_21_0.ppm the upgrade succeds but then will not start.  All I get is the splash screen and it hangs on Application Layer Started.....

I have uninstalled, restored back to 8000 and tried it again but it once again hangs after upgrading to SP1

What should I look for?