no sound with AXE I/O

[tzurby]

I suddenly don't get any sound with AXE I/O.
My system: Mac powerbook with Catalina.
Inputs and outputs are all set to AXE I/O.
Control Panel shows input. Amplitube 5 shows input and output signal.
But neither with headphones no with monitors I get any sound via AXE I/O.
Monitor knob to the right. Headphones to the middle. Master 3 o`clock.
Switching the Mac and Amplitube to internal headphone, there is sound.
USB cable must work, otherwise no input would be shown.
Firmware is up to date.
What to do?

[tzurby]

I have no idea why, but it works again...

[tzurby]

For whatever reason, in the systems setting of my Mac (Catalina) there is a "Tone aus" (probably "no sound") in the output section, which the system somehow engaged. Experienced mac users probably know that. I did not. Disengaging it gives the sound.
So, when there is no sound and you have a Mac, this could be the reason.