iMac Pro went in to Recovery mode after power loss during update, now won't even restore after DFU mode

OUCH

You mentioned " Reviving " and no success

May need the Restore as a last resort before venturing to the Apple Genius Bar

How to revive or restore Mac firmware

excerpt from above

" Restore "

Try reviving your Mac first. If your Mac can't be revived, follow these steps to erase it and restore it to factory settings. 

1. From the DFU window in the Finder, click Restore Mac. Then click Restore and Update to confirm. 
2. A progress bar in this window shows that the restore is underway. When the restore is complete, the affected Mac restarts automatically. If it shuts down instead, press the power button to turn it on.
3. If asked, select a Wi-Fi network or attach a network cable.
4. Mac with Apple silicon: 
   1. If asked, sign in to the Apple Account previously used with this Mac.
   2. When the setup assistant opens, use it to finish setting up your Mac. 
5. Mac with T2 chip: 
   1. The restored Mac shows a spinning globe as it starts up from macOS Recovery over the internet. Choose your language when asked.
   2. If asked, sign in to the Apple Account previously used with this Mac. Then click Exit to Recovery.
   3. When you see the list of utilities in Recovery, choose the option to install or reinstall macOS. 
   4. After macOS installation, the Mac restarts and opens the setup assistant. Use it to finish setting up your Mac.

Hey Bob — sounds like a rough update. If your iMac Pro with T2 chip won’t revive even via DFU from your M3 MacBook Air, and network restore fails, it’s likely the firmware got corrupted. The reset email from Apple (with proof of ownership) can help remove Activation Lock, but won’t fix the firmware issue remotely.

At this point, best move is to contact Apple Support directly for a Genius Bar appointment or mail-in repair — they may need to reflash the T2 firmware manually.

Thank you for the updated info