Hi @amarin27 - welcome to the community!

Unfortunately, by definition, any Flows triggered by a List Subscription can only go through the Flow exactly once.  You can see here in Klaviyo’s documentation:
 

Contacts can only receive a list-triggered flow once. If someone is removed from a list and then re-added to that same list, they will not re-trigger the flow. For example, if someone unsubscribes from your newsletter list and then re-subscribes, they will not receive the welcome series again.

• Guide to Creating a List-Triggered Flow

What I recommend is adding a hidden field and value to this new form like “sales-signup” with a value like “1” or “true.”  Then, create a Segment where Property of the User → sales-signup = 1.  Then create a new Flow that is Triggered on that Segment.  

In this way, new subscribers will go into your Main List and have that Custom Property.  Returning subscribers (who subscribe again) will have that new Custom Property.  Both will go into the Segment Triggered Flow to receive the first Flow email specifically for your Sale. 

Also remember, you may want to also put in Message Filter or a Branch Condition or a Time Delay if you don’t want net-new subscribers from getting the Welcome Flow First Email and the Sales Flow First Email at the same time (unless you want them to!). 

Thanks! So I think using the custom property and then using a segment to trigger is the best. 

Follow up question: 

I have created the hidden property on the submission button of the form and the form has been published. When I try to create the trigger on the flow and browse through the properties, the property I created does not appear. Do I need to wait until someone signs up? 

Hey @amadou,

You are absolutely correct! You can only create segments and filters rules off of dimensions and variables that have already been recorded within Klaviyo. This means that until someone has has filled out your form with the new property applied or if you manually applied the property to your own test profile, you would not see it as an available dimension. 

Adding to @retention’s great strategy, keep in mind that similar to a list triggered flow, segment triggered flows act in a similar way where it would only allow contacts to go through the flow once. 

David