REST API Call Is Returning 603 Error

[#1]

Issue

REST API call, Get Lead Activities, is returning 603 error

Solution

Error 603 refers to 'access denied' where authentication is successful but the user doesn’t have sufficient permission to call this API. Additional permissions may need to be assigned to the user role.
http://developers.marketo.com/rest-api/error-codes/

1. Go to Admin > Users and Roles
2. Select API User and identify what role it is assigned to (e.g. API role)
3. Go to Roles and check the permissions assigned to the API role
4. Check to see if the API role has 'Read-Only Activity' or 'Read-Write Activity' permission

In order to make a Get Lead Activities REST API call with the API user, the API role of the user must be modified to have permissions to  'Read-Only Activity' or 'Read-Write Activity'. If you use Workspaces and Partitions, make sure the API User has the necessary access to the workspaces/partitions being called.