If a zwave device stays “unknown” you should eventually delete the XML file in /var/lib/openhab2/zwave/ and try forcing the device to send NIF (triple-click the B button on FGR-222) if needed multiple times (check zwave logging).
In rare cases the device is unknown to the OH version you run, in that case try upgrading to a newer one such as 2.4M4, but be aware that this particular upgrade step comes with breaking changes to the ZWave binding.
