For Contracts for Salesforce to work with X-Author for Contracts, the XAuthorProduction remote site setting must be active. 

To Activate the XAuthorProduction Remote Site Setting

  1. In Salesforce, click the gear icon in the upper right and click Setup
  2. Search for "Remote Site Settings" in Quick Find
  3. In the list, locate the XAuthorProduction remote site setting and click Edit 
  4. Check Active
  5. Click Save