Hi Raul,
The steps or explanation shared here is only pertaining to cases where you have targetData personalization in email and you are trying to send proof using seed addresses
What is targetData personalization?
Normally on emails you will be using personalization data directly from recipient schema. Such personalization blocks will be like <%= recipient.firstName %>, <%= recipient.email %>
However, if there is some data which is inherently not available inside database marketers tend to generate that data on the fly.
It is done on the additional data section of a query activity or enrichment.
Suppose salutation was generated on the fly, the workflow will create a temporary structure to hold that data under column @salutation (this is configurable). Inside the delivery, you can use them for personalization by using <%= targetData.salutation %>
Now if you are trying to proof this delivery using seeds, you will have to populate the additional data section of seed with this wanted element so that the proofing can work.
Hence on the additional data section you define <targetData salutation=”Hi Sir” />
For this test, the delivery in my case is using targetData personalization, something like this <%= targetData.Survey_Unique_URL %>
So, my seed address have to have additional data containing <targetData Survey_Unique_URL=”http://www.adobe.com” />
You can change the url value as per your liking.
So I created a new seed address “Vipul Raghav” and configured it on the delivery.

If I send the proof at this step it will fail, the same that you have reported.
You will have to make the delivery believe that workflow is sending the same targetData to delivery.
As a result, I’ll just add a Query activity before it with a random selection query. Most important part is to provide targetData with alias name matching the field you need inside delivery. if you already have an actual workflow, you can skip this part.

Now open the delivery and send a proof and it goes out successfully.
Regards,
Vipul