Hi @nayanisakina99, welcome to the community!

There’s a few ways you can approach this. You can either add some Flow Filter conditions relative to a Date so new folks after the Date won’t enter the Flow. 

Or as @KatherineB suggests in a previous post, you can add a “Conditional Split” at the very top of the old Flow to stop people from entering the rest of the Flow. 

 See here: 

In either way you can keep all the Flow Messages Live while existing people complete the Flow, and the new profiles will go to the New Flows.  Once all the people in the old Flows have gone through, you can then turn off the Flow.

Hope this helped!

I have a similar problem to this, but can’t find the right thread as I’m sure this is common…

I forgot to make this live until today, and now I have 993 missed opportunities it seems.

Got it.

https://help.klaviyo.com/hc/en-us/articles/115002775272-How-to-resend-a-campaign-to-people-skipped-by-a-list-triggered-flow

You must send a campaign to reach these missed opportunities.