As you can see the subscription webhooks are not listed as option all though they are in the documentation.
My app has full access to the Subscriptions API's - I have been using it to create selling plans, etc. I've tried all api versions 2021-01 and above and am able to create other webhooks listed as options in the error. Is there another way I should be creating these webhooks?
I did not have the appropriate scopes for the shop I was working on. This was my first instinct but since I was able to create selling plans with no problem, I thought it wasn't the case. Upon further examination you only need write_products permision to create selling plans.