Some users may not be able to view/load the animated or static survey icons on their email due to Outlook settings and limitations. Depending on the Outlook version that they're using, they might see a play icon button or a click here to view the image.
There are three ways to get around this:
You could ask your customers to unblock picture downloads for all messages by adding your domain to their Safe Sender List.
You could switch to a static icon set.
Select Display text labels under rating images in the survey Publish tab. This adds a text link under each of the survey images in case they're not being displayed, or can't be clicked.