Due to their being no official PHP SDK, and the existing community SDK's not implementing JWT, I've started building my own.
After much battling I've managed to get the JWT auth set up, then I get the following error:
'Cannot obtain token based on the enterprise configuration for your app'
Currently the account is set up as 'OAuth 2.0 with JWT (Server Authentication)' with 'Application Access', all Advanced features enabled
Which settings am I missing? There doesn't seem to be anything obvious.