To troubleshoot this issue, follow the below steps:
Note: If the virtual machine is currently running and you do not wish to shutdown the virtual machine as you are not able to save anything, suspend the virtual machine and quit VMware Fusion.To do this, follow the steps below:
On the top left-hand side, click on the Apple Logo, click on System Preferences
Now go to Security & Privacy, click on Privacy and towards the left-hand side from the list of options, click on Accessibility.
Now place a check mark next to Fusion application listed for the Accessibility window.
If Fusion application is already selected, highlight the Fusion app.
Click on the " - " to remove Fusion. Click on " + " and go to Applications from the Finder window to select Fusion application. Click on Open.
Open Fusion and launch the Virtual Machine to use Mouse and Keyboard functionality.