Hi @BeenSun,
Welcome to the Community! We are so happy to have you! Sorry to hear about your issue, would love to offer a hand.
I think @Bobi N. brings up a great point that Double Opt in does require a second confirmation before it adds a subscriber to the list. However, if you have been confirming your subscription a second time, per your screenshot, can I ask when you turned your Flow live, meaning all the messages in your flow were turned from draft to live before you turned on your form? It could be that your Flow is still in draft form or was turned live after your you submitted the form.
Finally, a third option you could check would be if your Flow is connected to the correct List. I would dive back into your Flow and ensure that what triggers your Flow, on the top right side of your Flow builder screen, is being added to the same List as that’s synced to your form.
Thanks for participating in the Community!
-Taylor