Hi ​@Calder's Kitchen 

Thank you for posting in the Community!

I have seen that problem before - Try duplicating the pop up or editing the e-mail field and set the duplicated form live again. That should make it work. 

If it doesn’t work, you can make a flow, which trigger, when the metric “Form submitted by profile” and then include a “Add to list” module and then add the subscriber to the desired list in the flow. 

PS: Setup a trigger split, so it is only subscriber from the form with the specific form_id, which is triggering the flow.

Hope that helps! :-) 

Christian Nørbjerg Enger
Partner & CPO
Web: Segmento.dk
LinkedIn: @christianfromsegmento
Voldbjergvej 22b, 8240 Risskov

Adding to what ​@Christiannoerbjerg already mentioned, check to see if your List is double opt-in or single opt-in.  If it’s double opt-in, they won’t be added to the List until they click the confirmation message.  If your Welcome Flow is List Triggered, they will need to do this before they get into the Welcome Flow.

Also, double check if your Welcome Flow is “List Triggered’ when someone is added to a List, OR if you created a Segment and is Segment Triggered.  If it is the latter, you may want to check your Segment rules, and also note that Segment Triggered Flows can sometimes have a delay.

Lastly, just in case if you happen to be testing with your own email over and over again.  Note that neither a List Triggered OR Segment Triggered Flow will allow a Profile to go into it more than once.  So if you are testing this out, make sure to use different email addresses each time, otherwise it won’t work with the same email address!