After in-place upgrading of SCCM server to version 1706 all clients in the SCCM administration console are showing as offline. In the Configuration Manager Status Message Viewer there are many Message IDs 4951 and 1020 from the SMS_NOTIFICATION_SERVER component. Furthermore there is 0x80004005 error message in BgbSetup.log file.
SOLUTION
1. Open windows explorer on the SCCM server
2. Go to %WinDir%\Microsoft.NET\Framework64\v4.0.30319 folder
3. Make a backup copy of RegSvcs.exe.config configuration file (e.g. RegSvcs.exe.config.bak)
4. Edit the RegSvcs.exe.config configuration file by adding under the <configuration> the following 3 lines:
<runtime>
<loadFromRemoteSources enabled="true"/>
</runtime>
5. Restart the SMS_SITE_COMPONENT_MANAGER (Configuration Manager Service Manager)