same problem with 10.13.6 and 10.1.2
the recommended processes did not heal it - no usb access at all
message under security&privacy
"System software from developer "VMWare, Inc." was blocked from loading
does not disappear ...
so this worked for me - finally - and let the message disappear - and returned all usb devices:
"Thank you! I don't know why, but quitting all other applications and turning off WiFi did the trick. Weird."
after quitting all, WiFi off, disconnecting Ethernet aka WiFi cable ;-) the mouse click finally makes the message disappear.
found there "Allow" button not working when System So… - Apple Community