What's New In Coveo for Salesforce V4?
As of the release of Coveo for Salesforce V4, some changes have been introduced into the Coveo for Salesforce AppExchange package.
The most important change is the removal of non-Lightning Locker compliant Coveo components. For more information on the effects these changes may have on your implementation, see the upgrading from Coveo for Salesforce V3 to V4 FAQ.
When upgrading to Coveo for Salesforce V4, you may need to migrate some of your Coveo Lightning components. The Migrating Components from Salesforce API 39 to API 40+ article provides a detailed guide to help you with the migration process.