This error, LOGIN_MUST_USE_SECURITY_TOKEN: Invalid username, password, security token; or user locked out, means that the Salesforce credentials you have used for this connector use a security token. From time to time these tokens will need to be reset in Salesforce which we don't have control over.
If you would like to avoid using a security token in the future, please recreate your connector. You could then use OAuth to log into Salesforce. This would circumvent the need for a security token as it is a newer way to grant access. This authentication is not available on older connectors though, so you would need to use a new connector.
This doc should help you reset that token: https://help.salesforce.com/articleView?id=user_security_token.htm&type=0