The "generate" button doesn't work. There is no password history.
Chrome 64 and Firefox 58 both show the issue on OSX 10.13.3. Restarting the browser doesn't help. Rebooting the OS doesn't help.
Removing and reinstalling the extension has fixed the issue with Chrome (didn't try with Firefox), however this is the second time I have done those steps, and after the first time the generate password dialog stopped generating passwords and reverted to the old behavior after a day or two.