Create Webhooks API 400 Error

Hi Team, 

My team is building an integration with Bynder that, on install, is creating a webhook to sync assets/asset updates to our platform. 

We’ve hit an issue where, on calling the ‘create webhook’ api, v7/webhooks/public/api/subscriptions, Bynder returns a 403 error. We have ensured that our oauth app has create webhook permissions and the user authorizing does as well. Any idea what might cause this? Any guidance would be much appreciated!