Customer has added a state called 'Assign to helpdesk'. When he is trying to change the state, he is not getting the 'Technician/user list selection' to assign the record to a owner. Any configuration mistake causing this issue?

Customer would not have selected the ‘Inherited from’ drop down option while creating a state. Instruct the customer to select the ‘Inherited from’ as ‘Assign’ and then try changing the states. The user lists will be populated for the states which are inherited from ‘Assign’ or ‘Waiting for Approval’