After you upgrade to Configuration Manager current branch version 1706, clients may not be able to download content from peer cache sources. We have released a hotfix that resolves this issue. This is a targeted hotfix and will be available in the Updates and Servicing node of the Configuration Manager console for sites that need it.
For the latest information about the issue and how to install the hotfix, please see the following:
4042345 – Clients cannot download peer cache content in Configuration Manager version 1706 (https://support.microsoft.com/help/4042345)