Hello everyone,
I'm facing an issue when I want to send out an email containing a web app link (as a button) I created.
When testing in preview mode with a random test personalization. I can go through my email, click on the button to access the web app and it displays well.
The problem occurs when I try to send a proof to see how the render looks like and it seems that when I click on the link to access the web app, that window prompt with just an "ERROR" message instead of the actual web app :

Here are the delivery logs but nothing much to say about that :

Does this error happens to someone already when sending a test proof and have a clue on how to fix that ?
If you need more information for solving my problem, feel free to ask 
EDIT : I check both link in my preview (the one that work) and in the email (the one that doesn't work) and it looks like the URL that different. That should be the case, right ? Both version applies for the same customer.
Thank you in advance.
Kind regards,