There are two tables: Orders and Agents.
Each agent is obliged every day to create order.
As in any report, where there is a filter over a period of dates, show all agents, regardless of orders and order numbers if the order exists.
By default, when you select a date period, agents who have no orders in this period - hiding.
LEFT JOIN in the query - does not solve the problem.
Lookup Column - does not solve the problem.