ZBT-1 OpenThread firmware install fails

I’m trying to set up ZBT-1 as a thread router but it fails on the OpenThread firmware flash. I’m following these instructions:

And this is the error I get:

Failed to flash firmware
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/homeassistant_hardware/util.py", line 421, in async_flash_silabs_firmware
    await flasher.enter_bootloader()
  File "/usr/local/lib/python3.13/site-packages/universal_silabs_flasher/flasher.py", line 358, in enter_bootloader
    await self.probe_app_type()
  File "/usr/local/lib/python3.13/site-packages/universal_silabs_flasher/flasher.py", line 329, in probe_app_type
    raise RuntimeError("Failed to probe running application type")
RuntimeError: Failed to probe running application type

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/homeassistant_hardware/firmware_config_flow.py", line 203, in _install_firmware_step
    await self.firmware_install_task
  File "/usr/src/homeassistant/homeassistant/components/homeassistant_hardware/firmware_config_flow.py", line 310, in _install_firmware
    self._probed_firmware_info = await async_flash_silabs_firmware(
                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ...<9 lines>...
    )
    ^
  File "/usr/src/homeassistant/homeassistant/components/homeassistant_hardware/util.py", line 430, in async_flash_silabs_firmware
    raise HomeAssistantError("Failed to flash firmware") from err
homeassistant.exceptions.HomeAssistantError: Failed to flash firmware

Anyone have any suggestions on how to resolve?
Thanks