Membership unsubscribe button not working

I've set up Membership correctly (subscriptions are all being paid correctly), however when I test the shortcode [renewform] and I go to unsubscribe I get the following error on Paypal:

The unsubscribe button you clicked is invalid. You can find the status of all subscriptions in 'My Pre-approved Payments'.

Additional notes:

1. I've tried this but still not working: https://premium.wpmudev.org/forums/topic/membership-plugin-paypal-subscriptions-not-being-cancelled-when-user-cancels-on-site#post-516288
2. My Membership Gateway is set to Paypal Express Gateway (I only have that one active).