There are a couple of possibilities here. When a firmware upgrade fails, and the unit goes black (this is very common when users upgrade firmware without putting other devices into standby), and it disappears from xanbus, it is often still available. Depending upon how you upgraded, it could be easy.... If you used the conext combox, it's pretty simple. If you used the Gateway or the Config tool, it gets more complicated.
Did you use the Combox? If so, the inverter is still available in bootloader mode. You can fix it yourself - easily. I'm a long-time end user of the XW equipment, and I've had firmware upgrades fail in the past. The process is pretty simple.
If you used one of the other devices, you will have to go to the Schneider support website, and submit a service request. They will respond.