In the campaign creation process, there may be times when your campaign displays correctly in the Design step but then you see an error in the Preview step. See the example error below:
The typical cause for this error is an incomplete merge tag in the design. To fix the issue, go back into the Design step and confirm all merge tags have a beginning and ending set of %%. Then, hit Save and Next to make sure the changes took effect.
Please contact Support if you need help with fixing errors in campaigns.