Try clearing your cache or accessing HA in incognito mode (whatever your browser calls it) and see if they load. Sometimes the browser cache can cause issues like this.
Also negative. I created /www/ and placed files there. after confirming the files were there I restarted HASS but still no icons. I decided to reboot the RasPi, but that seems to wipe out the www directory. It’s gone completely.
I repeated this to make sure it wasn’t a fluke. Surely enough the www directory is scrubbed from the drive root upon startup.