Flexible Workflow Steps and Approval Logic

I person configured flexible workflow for acquisition requisitions. But erstwhile I effort to make a antithetic workflow done the Fiori APP "mange flexible workflow for acquisition requisition" and acceptable steps and delegate usernames, each users which are successful information valid effect successful an mistake successful the app : "Invalid Username". Can anyone assistance connected this issue?

I person besides different question:

It seems that we tin specify steps and delegate users to them. truthful what is the usage of the configuration node successful merchandise strategy (the past measurement successful acceptable up process with classification which is called workflow) wherever we delegate users to each merchandise codification successful merchandise groups? Is determination immoderate narration betwixt support steps successful workflow and and merchandise codes and merchandise groups successful merchandise strategy?