A VBIOS flash that went wrong leaves a card that will not post into any operating system. That rules out every Windows flashing tool, because none of them can run. You flash it from a UEFI shell instead, before Windows is in the picture.
Recovery only works if you have the BIOS that was on the card before you touched it.
Back up the VBIOS of every card before you flash anything. HiveOS will do it for you with a download button, and there are Windows tools that do the same.
Do that first, on every card, while they still work.
Download the UEFI build of amdvbflash and extract it.
Format a USB stick as FAT32.
Copy every file from the extracted archive onto the stick.
Copy your saved VBIOS onto the stick as well.
Rename it to bios.rom
Fit the bricked card and shut the machine down.
Power on and tap F11 for the boot menu.
Pick the UEFI entry for the USB stick, not the plain one.
List the adapters the tool can see with command amdvbflash -i
Confirm your GPU appears there. A Navi 10 card reports as Navi 10.
If nothing is listed, stop. The tool cannot flash a card it cannot see.
Force the flash with command amdvbflash -f -p 0 bios.rom
The force flag is required here. The tool refuses a normal flash because the card's current firmware does not check out, which is exactly the situation you are in.
The 0 is the adapter number from the listing.
Reboot with Ctrl Alt Delete when it finishes.
Boot into Windows and open Device Manager.
Find the card.
No warning marker against it means the card is back.
The UEFI build is worth using over the Windows executable even when the card still posts. It is more reliable on these cards.