Unexpected API Response - Box CLI

Hello, I'm using the Box CLI with a custom app using Server auth with JWT.

I've successfully done this in the past, but this time I've had to re-create the custom app and configure a new environment on my machine.

The environment configures, presumably correctly, my json file contains the public/private keypair, and client ID/Secret.

App auth level is set to Enterprise, and all Scopes/Advanced features are enabled

I have reauthorised the app after making any and all changes, and each time I try to transfer document ownership and/or delete a user, I'm presented with the following error;

Unexpected API Response [403 Forbidden | .02fe068d33dfe8d1b20bf9cc673f26f56]