@EnderXain 

some ONTs have the Ethernet port disabled by default and instead output thru Coaxial. 
Typically something to do with Moca networking and video/tv service I think. 
You may have to call the ISP to enable connectivity thru the Ethernet/Lan port. 

  @baracko_llama 

Thanks for the info but the port I used is working. An Orbi router was plugged into it and has been working just fine. Any other ideas? This ONT has several Ethernet ports btw. All of which are being used successfully.

  @EnderXain 

I have a FTTP connection via a ONT

This should work with the ER605 (mine does) but you have to setup your ISP as PPPoE with username / password which should be on your old router.  

The ONT is not a modem and wont dial the connection for you, its just a media converter in most cases.

  @Virgo 

I'm not sure what you mean by this? I unplugged everything from ONT except the power and fiber cable and plugged in the ER605. I even then did try unplugging ONT while leaving on the ER605 and it still did not work.

  @Philbert 

I was wondering this but my brother is the one who bought and set up the Orbi router and I do not think it is PPPOE.

  @EnderXain 

If you still have the orbi power it on and see what settings are configured for this, it may well be something he just done without thinking.. it would be unusual for an ONT to not require some username / password.  I know im my ISP (BT UK) its just a default username / password for everyone but it has to be there under PPPoE, only then will it connect via the ONT

On the ER605 can you post a screenshot of what the status is showing on the interface?  

  @Philbert 

The Orbi does not require a login. I just checked.

And the laptop running the Amanda software has

192.168.0.100

255.255.255.0

192.268.0.1

  @EnderXain 

Very strange..

If you click on the ER605 you should get a pop out on the right.    under DETAILS.. WAN  what is the status?   does it have an IP address and gateway?

Also under SETTINGS... Wired Networks...  Internet    have you setup the ER605 in here?   Try AUTO to start with

  @Philbert 

It has nothing under the WAN section and it says link down.

Yes I have been in this menu. Wan port is checked, online detection is custom at 10 seconds. WAN connection type is set to dynamic IP (the Orbi also had this setting). Use default MAC.