Flows in Klaviyo do not have an on/off switch. Each individual message in a flow has its own send status: draft, manual, or live. This allows you to build out a flow series and enable certain emails and/or text messages to start sending while still finalizing other messages you may want to enable later on.
If you would like to enable an entire flow to start sending, you will need to turn each message live one-by-one.
Turn a Flow Message Live
For each message in the flow you want to start sending, make sure you've customized and previewed the content and all settings. Next, in the lefthand configuration sidebar, click the Send Status dropdown and change the status to live. You will notice the icon on the card update to turn green as well.
Turning a message live means new individuals entering your flow will be queued up to receive this email or SMS message and it will send out automatically at the right time. Updating the send status won't affect anyone who might have received this message in the past.
If this message’s status was manual, and there are any recipients still awaiting review, those recipients will still need to be reviewed and sent manually. Messages marked for manual review are not sent automatically when the status changes to live.