The fact that you haven't had any answer to your question do far is because you posted it to the wrong place. You should post it to "products". Read this: Getting the most of the community when you have a Marketo question
You are providing too little info here for us to tell you where the error comes from.
It could be because your trigger campaign here is set to run only once. It could be because the link is the email is not set up properly (happens often if the URL is a token), ...
Can you see the link in the drop list in the "Lin" constraint if you trigger?
Thank you so much!