More often than not, the main reason your templates are not rendering is some sort of effect such as Bold or Italics were not correctly applied to a field that you are using in your message template. I.E. The double brackets {{}} were not included in the effect/
For Example:
Bad
Good
You'll notice that the Bold effect was added to the brackets {{}} on the "Good" example to ensure that the template would render correctly.
--
If you are still running into a rendering issue after double-checking all of the fields in your email template, please reach out to the support team via the Help Center and include as many details as possible. For example: The Email Template Name and the Deal Address you were attempting to use the email for.