By default, Notice availability is set to 24 hours. After this time, the Notice is no longer available on the app. You can change this to be available for one week, one month, or until a custom date.
If you have a Notice that you want to be available on your app permanently, select the custom date and change the year to one that's far in the future, such as 3000.
Once you've done that, hit 'Save' and your Notice won't disappear.