@ACupOfCoffee 

I found a thread last year where a user in Brazil tried to update the C20 and got an error. Turns out the firmware build was customized for the ISP which is why the update was failing when using the firmware from our official website.

If you looked at the label below the router and it shows version 4 with the country code being in the US, this may be a similar case with the update failure.

You could possibly try a older version to see if that works then upgrade to the latest.

@Tony I tried that and it didn't work. The firmware I'm attempting to install is the only one newer than the one already on there. Should it allow a downgrade?

@ACupOfCoffee 

Just to clarify a few things. The model you referenced says Archer C20, but you mention Archer A20. Given the build it is the Archer C20 correct?

Also, if you look below the router, does the sticker label mention the country code, something like (US)?

@Tony Sorry, yeah, it says C20(US) on the bottom.

@Tony I uploaded the firmware via TFTP. Now it just blinks. Think I bricked it?

@ACupOfCoffee 

Using TFTP is not the safe way to install a firmware so forcing it may have caused issues that the GUI was trying to prevent. I would probably contact the seller to see what can be done if possible.

@Tony Bummer, thanks

@Tony For future reference of people searching on hwre: OpenWRT totally worked and now the router is functional again.