How to Run Appian process from RPA?

Good Day Experts,

I'm trying to execute Appian processes via robotic processes and i'm using start process method under Appian service and i'm able to search my intended process model and its showing all the process variables but i'm not able to choose any value from the drop down ( drop down is empty). i've tried with adding an instruction and as well as by adding environmental variables but still value drop down is empty.

Can anyone please help me how to configure that?

thanks in advance.

Cheers,

Kalai.