@m.linney 

When a profile is already in a segment they won’t be triggering the flow. Or if people enter segment by you adding them with changing segment conditions also they won’t trigger a flow.

The only way people trigger a flow from a segment if they automatically on their own qualify to enter the flow, then enter it and will trigger a segment.

So the question here is are there people who were automatically added to the segment since you turned the flow live?

If not then that is the reason why no one triggered it. If yes then check maybe some flow filter is stopping them from getting it.

Thanks Bobi for replying so quickly!

Ah I see, so essentially, I should be configuring the segment definition after I make the flow ‘live’? That way they will get automatically added into the flow?

On another note, after asking this question I went in and realised there is a ‘Add past profiles’ option as well.

@m.linney 

Well actually no.. you shouldn't be editing configuration of the segment after the flow is live. That won’t help you add people to the flow. Segments as flow triggers only work if people automatically qualify (meaning they do something to meet the conditions of the segment organically) but not if they qualify by you changing the configurations of the flow.

So you should set up the segment as you like it to be and set the segment live. From that moment on every new person that enter the segment organically by meeting the conditions will trigger the flow and for the ones that are already part of the segment yes you have the option to Add past profiles.