Yes, I have opened a case with Symantec.
They have no workarround available so I went troubleshooting myself.
Recap:
No problem with SEP 12.1 RU5 and RU6 until I installed microsoft update KB 3125547.
After the install of KB 3125574 the SEP icon in no logner showing on the taskbar.
After Un-installing KB 3125547 the SEP icon is back on the taskbar.
AS KB 3125547 is a security update we need to install it.
So far a workarround is not available so I went looking for a workarround myself:
I found out that, after installing KB 3125547 you can edit the registry to make sure the SEP icon will show on the taskbar.
Registry setting adjustment:
First, make sure you CAN edit the registry as an administrator by changing the Tamper Protection setting in the SEP client:
Start the SEP client.
Goto change Settings – Client Management – choose the tab Tamper Protection – remove the mark at “Protect Symantec security software …”
Go into the registery (regedit) and goto:
HKLM\SOFTWARE\Symantec\Symantec Endpoint Protection\SMC\
Add DWORD registry value: LaunchSmcGui and set it to “1”
Don’t forget to mark the Tamper Protection again.
The SEP icon will be back on the taskbar.