After confirming I want to set WindowsHelloUnlock, I enter my PIN and receive this message:

Error saving the composite Key: Value cannot be Null
Parameter name:a

I use Windows 10 version 1909
I uses a master password along with a key file on a secure desktop to open my database.

EDIT: Solved the issue by going to Tools/Options/Security and add a tick mark beside "remember master password (in encrypted form)..."

Now the plugin works beautifully. Thanks!

My database is stored on ICloud but I tested with a copy on my desktop and got same result.