Ever since the latest update with Synapse 3, the program “experienced an error” and needed to be restarted (which always resulted in the same non-specific error). I tried uninstalling and reinstalling. That got Synapse 3 to load, but the Razer mixer would have a spinning icon that would never go away and the mixer would never activate.
Then I tried uninstalling and installing Synapse 4. It loads, but then as soon as the Razer mixer has finished loading Synapse 4 will crash every time.