Migration SEP 12 RU2 to RU4 client packages not upgraded

Hello,

I upgraded on our Server 2008 R2 SEPM from SEP12 RU2 to RU4 without any problems. Windows 7 Clients are communicating with SEPM, receiving updated definitions etc., everything runs smoothly and normal.

BUT, clients are not upgrading from SEP 12.1.2015.2015 to 12.1.4013.4013.

In C:\ProgramData\Symantec\Symantec Endpoint Protection\12.1.2015.2015.105\Data\Logs I find the message: "download of new package 12.1.4013.4013 failed".

Any idea would be appreciated as I don't want to install the package manually on all our clients.

KInd regards AL