When accessing Veeva functionality that requires pages to be loaded from an S-Control or VisualForce Page, the end-user encounters either of the two errors:
No message body writer has been found for class com.veevasystems.api.response.ErrorResponse, ContentType: */*
Error establishing connection to Salesforce.
In most cases, the error occurs if the API Requests has reached the Org's limit.
If the API Request limit has not been reached, the end-user needs API access to utilize certain functionalities within the CRM Online application.
Provide API Enabled System Permissions for the user either through the Profile or designated Permission Set.