Hello @Anthony Lyon and welcome to Microsoft Q&A.
I believe the cause is an unregistered Event Grid. Event Grid is the mechanism which notifies ADF of storage events.
The integration described in this article depends on Azure Event Grid. Make sure that your subscription is registered with the Event Grid resource provider. For more info, see Resource providers and types. You must be able to do the Microsoft.EventGrid/eventSubscriptions/* action. This action is part of the EventGrid EventSubscription Contributor built-in role.