@aina 

Flows don’t work like that. That is why we have flow TRIGGER.. when it comes to lists or segments the trigger is when someone is added to list or segment. And because when you created this segment the people were already in it they wont trigger the flow. The only people who will trigger the flow are new people that will enter in that segment..

How we usually set up Win Back flow is.. trigger placed order and flow filters placed order zero times since starting this flow, also you can add flow filter or email filters has never been in this flow or email filter has never received this email before  if you want.. and than before the first email add 180 days time delay

so when someone place an order they will enter the flow.. than they will wait 180 days to receive the first email, but they will only receive it if they haven’t placed an order in that time while they were waiting.. 

Thanks for the great insight @Bobi N.!

@aina, using the Placed Order metric event as the flow trigger versus a segment trigger would be best practice for a Winback Flow not only for the reason of what Bobi had mentioned of the flow only serving to customers who are newly added to the segment; but also because segment triggered flows are only served to customers once. Metric triggered flows would serve to customers as many times as they take that specific action; in this case, making a purchase. 

I would recommend taking a look at the following article and guides Klaviyo offers on building Winback flows:

• Creating a Winback Flow

• Objective Video: Turn On a Winback Flow

Hope this helps!

-David

@Bobi N. @david.to This makes much more sense now. 
Thanks so much for the helpful information! :)