If you accidentally archived your pool, you can easily unarchive it:
Log into your commissioner account
Click the Pool Memberships link at the top right of the site
Scroll down to expand your archived memberships at the bottom of the list
Click Options next to the archived pool
Select Unarchive
Your pool will then be active again, and members will be able to join.
If you need any help with this process, feel free to contact support@runyourpool.com!