Model :

Hardware Version :

Firmware Version :

ISP :

I have a Archer C9 v3, which I allowed to upgrade to the then-latest firmware (1.3.0 Build 20161018 rel.71163(4555))

This firmware doesn't seem to be available now, but the 1.2.0 software is (Archer C9(EU)_V3_160713).

But I can't 'downgrade' to it (I've tried using the Web UI and the tftp firmware recovery:
The WebUI gives up quite quickly saying: Unable to upgrade.
With tftp it copies the firmware across, reboots, but the 1.3 firmware is still running.
)

I'd really like to get the DD-WRT firmware running on it. Beta firmware is available and other people have it working on the C9v3, the upgrade process (WebUI or Tftp) behaves in exactly as described above for the TP-Link firmware.

Q: Is this the firmware lockdown that is mentioned?
Q: Is there a way round it?
Q: Is there something else I can try?

Thank you.