Thank you.
But the problem is not the keyboard per se. An POK footswitche would also not work.
Because we are in germany our 11 computers are running with a "german" windows version (Windows 10 x64).
The problem is the german windows version.

So we have this problem on 11 laptops and computers.
From that 8 laptops are recording tapes and vinyl around the clock.  
Until this is fixed we use [ALT]+J+K
 

Using a POK combined with a program caled Bome Midi Translator you can map any key/pedal to virtually any command, inside or outside of Sonar.  I use it both in the studio and for live performance. It is incredibly useful. Not sure if it will solve the German windows problem though.

THambrecht
With the new November 2016 update it is no longer possible to create any shortcut for "insert marker".
The shortcut in the helpfile don't work. And I'm not able to create any key for this command.
For example : Ctrl+J  == Project | Insert Marker
We need to create markers hundred times the day because we digitaze tapes, vinyl on several notebooks and give the recordings descriptons with the markers.
But these computers have german keyboard layout - but Sonar runs always in English.
 

Are you using a different computer keyboard layout or is the layout mappings from the OS?
Would like to try and repro what's going wrong so we can address it.
 
Of course you can change SONAR's display language via Command Center settings.  Just pick German from the dropdown and then reopen SONAR.
 
Keyboard input would likely be set in Windows Control Panel.
 
Let us know.
 
Keith

On my German Win 8.1, M stilll works for inserting a marker for SP 11/16. Also, German and English keyboard layout are the same for M (and all other letters except that Y and Z are switched), no idea why it should no longer work due to keyboard layout. Are any other shortcuts affected?

The 'Marker' button on my VS100 has stopped working since the update, too, so I think there IS an issue here.  All the other VS100 controls as normal - transport, mute, arm etc.  Keyboard shortcut m is still functional here, though (I am in the UK).  Any other VS users experiencing this?

Same for me. M does not insert a marker since the update. I've also tried assigning other keystrokes to perform this function, but nothing works. Hope this gets fixed soon - it's lack of function is very annoying and workarounds are less useful to me.

Simply hitting M has and continues to work over here...

I have a number of keys remapped to emulate older versions of SONAR (e.g. F9, F10 for marking regions, M to mute a clip), including F11 mapped to Insert Marker.
 
Most of my remapped keys are working as expected, except that Pressing F11 no longer inserts a marker. After the update, the mapping appears to have reverted to its default of M, although the context menu still shows F11 as the shortcut.
 
I have re-bound M to Mute Clip as before, so it now works again. However, F11 still does nothing.
 

M to insert a marker is not working for me here in Statesboro, GA, USA.  Seems it was working until 2016.11.  My mapping says it's bound.  I unbound and bound again and M is still not inserting a marker.

M for marker is still working for me. I skipped the October update so I went Sept. to Nov.