API, WebHooks, trial account and n8n

I've been working with our ServiceM8 demo account and n8n. I've successfully got n8n to work when pushing into SerniceM8 e.g. running a node such as "Queue Job" etc.

When listening for changes in n8n e.g. with the ServiceM8 "Job Details Modified" node, there's complete radio silence. I've also been unsuccessful when it comes to adding WebHooks i.e. creating a WebHook subscription via https://api.servicem8.com/webhook_subscriptions/object.

I chose to switch to a live paid subscription to test and everything instantly works.

Does anyone know if there are restrictions on the demo account?