After upgrade to 2016, can't view SQL Server Logs Just upgraded to SQL Server 2016 from SQL Server 2014 SP1 CU4. 

This is a clustered instance

I am no longer able to use xp_readerrorlog and xp_enumerrorlog

Msg 22004, Level 16, State 1, Line 10
Failed to open loopback connection. Please see event log for more information.
Msg 22004, Level 16, State 1, Line 10
Error log location not found.


Found this link:
Unable to open SQL Server Logs


I can open the error logs manually via file explorer
The startup parameters for SQL Server Service indicate the right
location for the error logs.
Running repair on the instance didn't resolve the problem
Disabling Shared Memory for the instance didn't resolve the problem.
rebooting after all these issues and repairs didn't help
No aliases are being used to connect to this instance
127.0.0.1 is in the hosts file


Basically they are saying to repair the instance. 

Any other options?
Windows patching and majid's solution is what worked for us too. Just adding my 2c that may help others. We have a cluster with 2008, 2014 SP2 and 2016 CU2. After upgrading an instance to 2016, we had the following errors:


2014 and 2016: syspolicy_purge_history job failed on step 3
2016: SQL agent would start then stop
2016: Couldn't view SQL error logs


Windows patching, which primarily applied .net security patches fixed the syspolicy_purge_history job in 2014. The new ODBC driver fixed remaining issues in 2016.

Note: installing 2016 SP1 before installing this driver (https://www.microsoft.com/en-us/download/details.aspx?id=53339), will install a newer ODBC driver, that appears to have the same issues when running on a cluster. We attempted this on a test environment, but had to uninstall SP1 and the new ODBC 13.1 driver, then install CU2 and the other ODBC 13.1 driver. Haven't attempted to install SP1 again yet