"Conga Courier has attempted to scan your Salesforce.com instance but could not, because of invalid credentials on the Setup page. Further delivery of scheduled reports will not resume until the problem is resolved. Please login to Salesforce, choose the Conga Courier application and then the Setup tab to correct the username and password for Courier to use.
INVALID_LOGIN: Invalid username, password, security token; or user locked out."
This occurs when your Salesforce.com login credentials are incorrect.
What To Do
To correct the issue, check that you are using the correct Salesforce login information.