Try and open a VM:

Could not open /dev/vmmon: No such file or directory.

Click Ok

Please make sure that the kernel module `vmmon' is loaded.

Click Ok

This just started happening when I try and open a VM from Fusion 8.5.10.  Uninstalling and Re-installing VM Fusion doesn't help.  This is on a Mac (Mojave OS).  Also don't get anything in Security and Privacy in Mac like I have seen on other posts.