All contests in a League need to fill up in order to run, unless you have set the contest to be resizable. 

If a contest is resizable and doesn't reach the initially intended number of entries, it'll be automatically resized to the current number of entries it has. This only applies to contests with fewer than 200 entries.

• Learn more about the resizing rules.
• If a contest is non-resizable and doesn't fill before the lock time, all entry fees will be refunded.