Thank you for the answers, unfortunately the problem exists, but now I have a hint.
On this computer there is Win7 Professional without Windows Media Player.
I have installed VLC and Foobar to try to play wma with them, but they were not able to play wma either!
The files are good, because an another computer can play them with Windows Media Player.
Before it I had Win8.1 and MC could play these wma files.
Is the problem in connection with Win7 Professional?