@shawnsbrain66 

In this case, I AM the ISP.

They did send me the firmware, but there is no place to install it that I can see.

@shawnsbrain66 

I'm in the same boat as you now, but cannot get tp-link support to send me a firmware for the device. Do you still happen to have the firmware they sent you and could share it?

@Valgar 

https://www.dropbox.com/s/rcvxkref9lon44k/EC330_G5uV1_US-up-ver1-0-0-P1%5B191030-rel13523%5D_beta_2019-10-30_14.09.17%20%281%29.rar?dl=0

@shawnsbrain66 you put the file on a USB than got to system tools go to firmware update then browse for the file on the USB

@shawnsbrain66 

You are a LIFESAVER!

So the best way I found to install the firmware if you are locked out and unable to do anything with ACS.

1) wire directly to one of the ethernet ports and set your system interface to a 192.168.0.X address
2) start a ping to 192.168.0.1 from a terminal 

3) press and hold the reset, whilst powering on the ec330-g5u

4) if the stars align, you should start getting pings to 192.168.0.1

At this point you can get to 192.168.0.1 from a browser and it should state that the router could not start, and to install/upgrade firmware. I extracted the rar and used the gui interface to upload the .bin.

After that, it rebooted (pings stopped, although the "install" counter was only around 50%), and then I was able to get to 192.168.0.1, set a new password, and restart the setup process.

Cannot thank you enough for this!