In DTM, you'll want to set a rule that triggers the event in question, as well as providing a unique value in the 'serialize from value' field. The setting 'use event ID' means that an event will not send data to Adobe Analytics unless it is accompanied by a unique value.
Typically the field 'serialize from value' is a data element captured elsewhere on the page. If this data element sends a duplicate value ever, those duplicate values don't record the event.
Client type data element will return new or returning, everytime after an order is placed. So if 3 new customers A, B, C are coming one after each other and place an order, the will get the value new and Orders by new customers event will not record anything?
Which means that instead of setting "use event ID" I should choose "always record event".