If any changes were made to the campaign after the test was sent, but before the recipient viewed it, the links will then be invalid.
As test campaigns are dynamic, as soon as a change has been made to the campaign, links will no longer work nor will the web version of the campaign. The cause of this is that when the campaign is changed, the system regenerates the URL information and replaces the old - thus invalidating the test campaign links. Changes can include:
- Modifications in the Settings step
- Adding or removing Recipients
- Adding or removing Files or Links
- Modifications in the Content step
After you have completely finished updating your campaign, if you send another test, the links should work fine.