Hello Ossian,
The warning informs you when any portion of the signal is greater than the reference level. Typically to warn users when they are approaching compression or when the measurements are being drawn off screen. For the whole trace to not appear on screen with that warning can be the result of a couple things. Is it possible the entire trace is higher than the reference level? This is possible if you accidentally set the reference to a very small number. You can click anywhere on the screen to see a marker reading. What does the marker read in amplitude? I remember you were looking to install a USB card in your PC. It is possible invalid values are being returned to the PC creating bad numbers as well, potentially due to some incompatibility with the card you were installing.
Regards,
A.J.
