Yesterday suddenly the info on my screen is no longer visible, for example PH, Redox values. When restarting, the GHL logo, etc. is visible, but as soon as he has to load values, the screen is dark / black. I can access the profilux via USB / Web so it just works, all calibrate etc. can only be done via the buttons. What have I already done: reset, reload firmware everything to default settings nothing helps, any idea what else I can do?