OAUTH2 Generic Rest API set up

Hi All

This is my first time setting up OAUTH2 in LibCre.

I have set up the server side to accept the application onmats redirect_uri and added in the ID and secret and auth and token URLS but I keep hitting an error - invalid client.

This is after I have authorised the site to access.

The get token post requires a code value (returned from the authorize request) but I cannot check it has received anything.

Is there a way to debug this a bit more (see the connection payloads and response?)