You should be able to resubscribe at any point by following these steps:
- Click your profile icon in the top right corner
- Select the Update Plan button and toggle the Monthly or Annual option at the top
- Select the button under the tier you'd like to upgrade to
- Enter a payment method if there isn't one already
- Click Subscribe
If you aren't able to log in for any reason, you can reset your password by following the steps outlined here: Resetting your password