You see an error if you click View Redlines or Send for Negotiation in Conga Contracts for Salesforce for Salesforce. You might see the following errors: Unable to compare selected documents or Your email message was not sent.
The maximum number of OAuth authorization sessions was reached. Users can have no more than four OAuth authorization sessions working in a given environment. When a fifth session is kicked off, the first OAuth session is revoked.
It is also possible that the user who initiated the OAuth session was removed from the system.