Error Message: “CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY, esign.Document: execution of AfterInsert caused by: System.EmailException: SendEmail failed. First exception on row 0; first error: SINGLE_EMAIL_LIMIT_EXCEEDED”

You could see this error message when trying to send a document for eSignature and you may have hit your Salesforce daily limit for sending email. You will need to check if you hit this limit and then either make changes to your process or Salesforce settings to work with this limit or submit a case to Salesforce support to request an increase on this daily ‘single email limit.’