Hello vkum,
As i understand it, direct contribution relates to the contribution from the analyzed process. If you analyze diesel burned in agricultural equipment, there is a lot of direct contribution due to the emissions from the process. IF you make your own process with no elementary flows, there is no direct contribution from your process. If you have a process that models a life cycle, or that gathers inputs to gate for a company etc., there might not be any direct contributions that are not covered by other processes.
If you have elementary flows in your process, and the analysis still shows 0% direct contribution, i do not know the issue.
Best of luck