Damian,
I would first recommend that you please click 'check otk' and all sync buttons on the gateway plugin page (/admin?action=PLUGIN-lrsgateway), note all errors and attach the catalina log here.
Some additional information to take into consideration:
Under the "Authenticate APIs" section of the API Portal wiki:
https://docops.ca.com/display/APIDP35/Authenticate+APIs
There is a note about integrating with OTK:
"Note: Before you can use OAuth authentication, The CA API Gateway Administrator must install and configure the CA OAuth Toolkit (OTK) on the CA API Gateway and then integrate the OTK with the API Portal. For more information, see CA API Gateway OAuth Toolkit."
That links you to the OTK main page, and there is a sub link titled "CA API Portal Integration", which takes you here:
https://docops.ca.com/display/APIMT10/CA+API+Portal+Integration
I hope that's the information you are looking for. Let me know if you have any additional questions
Sincerely,
Stephen Hughes
Director, CA Support