Start Form won't invoke on Process Model Tutorial

Hi,

I am stuck on the Tutorial in the Appian Developer Course - Tutorial - Building a Process Model. 

Basically, Start Form will not invoke on the HR Application, Tried vehicel Management Tutorial and same issue, Process Model runs, no errors but start form won't open and accept data to store.

All expressions/parameters/DB's etc triple checked and accurate but can't for the life of me get the start form to open....

Any ideas?

Thanks

Mark