Overview - Receiving a successful response from the Marketo API however, the response body returns a 603 error code with Access Denied.
Cause - The above 603 error is returned from Marketo when the authentication has been successful but the user doesn’t have sufficient permission to call this API.
Resolution - This can be resolved by logging into Marketo and following the steps below.
- Go to Admin > Users and Roles
- Select API User and identify what role it is assigned to (e.g. API role)
- Go to Roles and check the permissions assigned to the API role
- Check to see if the API role does not have 'Read-Only Activity' or 'Read-Write Activity' permission
Further information can be found in Marketo's public documentation here.