Hello Daniela,
Yes you’re right, the second new member will not get the pop up because the browser saved the flag.
It also wont act as you wish if the old member opens his account from new browser, right ? local will not be the same as the first browser he used. So, better way to do is to create new item in the Data Base with Boolean value and then you only check if its true or false to show/not show the pop up and change that value after showing it.
Hope this helps you.
Best,
Mustafa