When you create a contest you must specify the start and end date. If you don't specify these dates, when you try to view the contest page you get this message. To quickly fix this error all you need to do is:
- Go to Contests
- Click on the edit link below the contest name.
- Scroll down until you see Schedule
- Change the start & end dates. Make sure the start date comes before the end date.
If after changing the start & end dates correctly you still get this error message then chances are that you have a cache plugins installed such as:
WP Super Cache or W3 Total Cache
You need to disable these plugins or exclude the contest pages from caching the contest pages.
As soon as you disable these plugins or exclude the contest pages from the caching, the error will go away.