A 1018 Marketo error is thrown in the Marketo Admin Notifications if clients enable "read-only company" when it is not applicable.  The Marketo Company and Opportunity APIs are only available on instances that are not currently synced with a CRM such as Salesforce or MS Dynamics.  If a client's Marketo account is synced to a CRM they will need to un-check the 'company' and 'opportunity' API permissions in Marketo, and make updates to Company and Opportunity information through the CRM rather than the API.

Note that this 1018 error is not passed through to SAP Open Connectors and is only visible through the Marketo Admin Notifications.