This is a fairly well known problem which I first saw with guests running OS X 10.10 Yosemite, and in a later update of VMware Fusion it also affected guests running OS X 10.11 El Capitan.
There is a compatibility problem between VMware Fusion's USB support and some older macOS versions. The solution: go into the settings for the virtual machine and change the USB settings to disable USB 3.0 and force the VM to use USB 2.0.
Details are in this discussion thread (and probably several others):
https://communities.vmware.com/t5/VMware-Fusion-Discussions/Keyboard-Mouse-not-working-in-Yosemite-V...
