On Linux CrossOver needs a working X11 windowing system in order for Windows applications to be able to bring up a graphical user interface. In other words, if you get this error no Windows applications will work.
If you have any of the missing 32-bit libICE, libSM, libX11, libxcb or libXext warnings, fix those first as they all break X11 thus triggering this warning too.
In all other cases please file a support ticket so we know about the issue and get a chance to help you.
Fixed with CrossOver 12.2.1
This warning was also known to happen when running CrossOver 12 on SUSE systems. We have preserved this workaround for corner cases but recommend users upgrade to the latest version of CrossOver. You can work around this issue by first running the following command before starting CrossOver: