I want to send out a customer voice survey to accounts in Dynamics 365. I have set up the link as a button and linked to the correct survey. When I sent out the email (real send not test send) the button was not present. What am I missing?

I want to send out a customer voice survey to accounts in Dynamics 365. I have set up the link as a button and linked to the correct survey. When I sent out the email (real send not test send) the button was not present. What am I missing?