How to recreate 'Cancel My Registration' button on Events through the API

Hi,

We're looking to find the endpoints that sets a member that has already registered+paid for their event to CanceledPendingCheckout and also pushes the refund amount to their cart.

I've tried the _execute + CancelEventRegistration endpoint but this skips the step where users have to submit their cart to complete the cancel.

I've also tried updating their current EventRegistration to CanceledPendingCheckout using the put /EventRegistration endpoint but this does not seem to update their status.

Are there any previous/further steps i'm missing for either of those endpoints to work like the out of the box button?

Thank you,
Jesus