Woocommerce Subscriptions 2.1.4 Compatibility Error? Help!

Hello!
In light of the new version 3.0 of woocommerce, I realised I was having trouble getting Woocommerce Subscriptions 2.1.4 to work. What version of Woocommerce works with Subscriptions 2.1.4?

It all works fine in the admin until it gets to the client side. When entering the checkout, I get an error in a loop above the forms for the details:

Warning: array_merge(): Argument #1 is not an array in /var/sites/h/helensbayorganicgardens.com/public_html/wp-content/plugins/woocommerce-subscriptions-2.1.4/includes/class-wcs-cart-renewal.php on line 432

Warning: array_key_exists() expects parameter 2 to be array, null given in /var/sites/h/helensbayorganicgardens.com/public_html/wp-content/plugins/woocommerce-subscriptions-2.1.4/includes/class-wcs-cart-renewal.php on line 436

I tried downgrading to a few versions of woocommerce to 2.6.x but the subscriptions tab disappeared in those versions and I could no longer find settings for it = essentially innactive while being “active”.

Has anyone encountered these issues? Maybe I need to wait until it’s updated, but I wanted to make a demo for a friend without having to pay for it.