There are many version of the FE599 sold over the years. The original Z-wave FE559s Do not work with the latest firmware and the firmware on the lock cannot be updated, mine are the v1 version and the only controllers I have found they will work with are the Concord 4 z-wave control with Alarm.com (and only will work then if there are no-neighbors talking between them, I only have my Locks and Thermostats on that z-wave mesh, all my lights are on the Vera), and Nexia Bridge (which would make sense because they were designed for the Nexia Bridge). They do work with Vera on older Vera firmware but not on the newer "self heal" version of the UI7 firmware.
Newer version of the FE599 do have updatable firmware but they can only be updated if you have a Nexia Bridge (which requires a monthly fee, however, if you buya Nexia Bridge you get a month free and can then cancel which would allow you to update the firmware, assuming you have a newer version of the locks and not ancient ones like mine, you might be able to get your locks working if you buy a Nexia Bridge and update the lock firmware, bad news is you don't know if you have updatable firmware version of the locks until you try it!).
the FE599 is not a z-wave plus device, and firmware alone won't make it z-wave plus compatible but z-wave plus isn't required to get it work. The latest versions of the FE599 do seem to work with the Vera Plus. So it is really just going to depend on the age of your Z-wave locks. If you have really old versions they are only going to work on UI5 or older version of UI7 They will not work with Vera Plus since it comes by default with the self healing firmware that doesn't work with the older locks.