Preview emails may not be sent for a variety of reasons. These are some to consider:
1. Does your newsletter have enough content?
The most common reason for a preview email failing to generate is a lack of content. First, check your article settings on the Design page to see what your minimum article count is set to. If the number of articles on your Upcoming Content page does not meet your required minimum, you will need to either adjust your settings or add more content.
2. Does your newsletter have a subject line and a title?
These are both required fields to send both preview emails and newsletters. You can edit your newsletter title under the company name here. You can edit your subject line here.
3. Check your SPAM folder!
Your newsletter might have gone to SPAM, especially if you are not sending from your domain! Check out our documentation on Domain Authentication for more information.
If you have reviewed the above tips and still don't know what caused your failure to send, please contact support.