Have you noticed that the fancy button in the immediate email of your DFY campaign isn't clickable anymore?
Most of the time, when you've done lots of changes to that button apart from just changing the assigned page shortcode, the clickable attribute of the button will be nullified so it ends up non-clickable anymore.
The FIX is actually very simple. If you have another campaign that contains a similar working button in its immediate email, go ahead, edit the campaign and copy the button in its immediate email by highlighting it and pressing CTRL + C (or Command + C on a Mac device) - you can also just right-click it once highlighted and click on "Copy".
Once done, go back to the Immediate Email of the campaign that you're trying to fix, then delete the existing button there and paste the one you copied from the other campaign by either pressing CTRL+V (or command + V on a Mac) or just by right-clicking on that area then click on "Paste". You should see the button again by then. At that time, you want to grab your coupon's page shortcode again and replace the existing shortcode that's in there.