Sends a triggered email to a contact is not working with all emails

Question:
I am sending triggered email (wix-crm-backend) to contacts’ on my website but the emails are being sent to some email address but not other.

For example:
The email is being sent fine to my personal email: abosriex@gmail.com
But not send to my profissional email: abosriex@materialise.be (I am getting the following message instead - " Not Found: the requested item no longer exists")

Product:
wix-crm-backend → Triggered Emails Introduction | Velo

What are you trying to achieve:
I get the name and email address from the user and add them as new contact then I trigger email using contactId

What have you already tried:
I already sent to support but they directed me to the community forum. However, I am not able to see related topic.