Perspective "Sessions Exceeded" in Edge 8.0.12 with only one open session

After I install ignition edge 8.0.12 I try to open a perspective session but get following error:

The number of running client sessions has exceeded the permitted number.

Of course this is the first perspective session and I don’t open any other sessions or even vision client or designer at the same time.
So I wonder why I get this error.

Did you change the default visualization mode? Edge can only use one visualization module at a time (either Vision or Perspective). See more about this here: