On 04/10/2016 11:45 AM, L.S.-Soc&Gam wrote:

[...] 
I checked my version and it is the very same as yours.
Can you maybe give me the code that you tested, to create a matrix, so I 
can copy paste and test it?
Because I entered a simple matrix again and still the finished pdf only 
shows empty braces....

Hi Sebastian,

I copied and pasted your code adding \starttext...\stoptext:

    \starttext
    \startformula
    S=\left(\matrix{
      \sigma_x & \tau_{xy} & \tau_{xz} \cr
      \tau_{yx} & \sigma_y & \tau_{yz} \cr
        \tau_{zx} & \tau_{zy} & \sigma_z \cr
    }\right)_{xyz}
    \stopformula
    \stoptext

My guess is that the different results may be related to the OS.

I’m on Linux 32bit using luatex-0.90.0. As far as I know, Windows is
provided with luatex-0.95.0.

This might be the cause of the different results. But it is only my
guess. If this is the cause, you may have found a bug in luatex-0.95.0.

I hope it helps,

Pablo