Apple Keyboard and KVM switch works with one MacBook Pro, but not another.

I have an Apple wired keyboard (A1243) connected to a KLau 4 port KVM switch. I have a 2023 M2 MacBook Pro (Ventura 13.5.2) connected to the switch. Both mouse and keyboard work perfectly. However, I also have a 2019 MacBook Pro (Ventura 13.5.2) connected to the switch, and only the mouse works. Both mouse and keyboard work with the other two systems on the KVM switch (a 2010 Mac mini and a Windows 10 machine).

Only the 2019 MacBook Pro has a problem with the keyboard. Any ideas?