Unable to cancel Stan subscription via Apple's Manage Subscriptions

I am trying to cancel my monthly subscription to Stan via manage subscriptions in Apple. I can get to the box with the button to confirm the cancellation and it doesn't do anything. I've tried directly within the Stan platform & it says my subscription is managed by Apple & to do the cancellation there.

[Edited by Moderator]

Original Title: how to cancel my subscription to Stan which was purchased via Apple. I have tried via manage subscriptions but the cancellation button doesn