VST3PluginTestHost for debugging

In the past I used VST3PluginTestHost for debugging with no problem except that there is no MIDI-out option.
Today I tried the new VST3PluginTestHost and the process routine is not called, so no more debugging is possible. What could be the reason?

Sorry it was my fault. For some reason I wasn’t able to push the start button. without it no process is done.