User is unable to send or receive messages owing to insufficient privileges.
The user does not have appropriate permissions to create SMS records.
A minimum set of access is required to send and receive text messages. Refer the section on SMS-Magic Converse Permission Details in the SMS-Magic Converse Guide for Salesforce Admin following link to review and grant appropriate access.
You can also grant the SMS-Magic Permission sets to users.
The Permission Management section under Converse Settings provides the details on available permissions.