Since some time there is but the blue or green patterns indicating that there is some sound are showing up.
Up to now it worked well and I have not changed anything.
Thanks for some help,
Windows7 64 ram 8gb
sound card Babyface
This is definitely the most common question on this forum. Use the getting started included pdf and check your connections. Probably the first thing I would do is make sure your system’s sound isn’t muted. 
What are you recording with?
The problem is solved. The file that I tested had crashed Cubase but apparently kept on working, so there was no sound even when I reopenned it.
I also had to increase the sound level of a window of my sound card for an other reason, which explains why the other files also seemed to be silent.
Thanks.
Great! If you have a similar problem again, you’ll want to make sure that no other apps are open. My next guess would’ve been that another program was using your soundcard’s output. 