You can check if there is a DHCP by changing DHCP from auto to static with the following setting:
IP Address: 192.168.0.222
Subnet Mask: 255.255.255.0
Primary DNS: 192.168.0.1
If that does not work, you DHCP may be fine but DNS may be a problem, so change the primary DNS to 188.8.131.52 and see if that fixes the problem.
Good Info. So you are connected by cable (wired) at the moment. The settings you listed all look fine but you can try change them as @YetAnotherAcc suggests on the TV settings. Making them STATIC (Fixed) means the TV is set to always use the same numbers to connect to the modem. It might resolve the issue.
Note instead of 184.108.40.206 you could also use 220.127.116.11 in Primary DNS.
Do you have anything else plugged into the Optus modem via wire? (Not counting the NBN modem)
Understand you might not want to experiment while its working but if it goes off again then perhaps try the static settings on the TV as suggested and then try turning the TV off and on a few times (at the wall?) to see if it now retains its connection.
Note that I edited my post to change the IP from Address: 192.168.0.3 to 192.168.0.222 . That's to eliminate (in practical terms, although not 100% guaranteed) an IP address clash that might occur.
With a low IP subnet (x.x.x.3) the DHCP server might allocate it to another device if the TV is off when its IP lease expires.
With a high IP subnet (x.x.x.222) the DHCP server is very unlikely to allocate a number that high to another device, no matter how long the TV is turned off , unless you have a truckload of devices trying to connect to the router, so a IP clash is very unlikely to occur.
This also should eliminate the need to mess around with settings on the router itself such as allocating the static IP address there or to changing the DHCP subnet range to exclude the static IP address you assigned on the TV.
You can't do any harm by making these IP changes and they can all be undone by simply changing DHCP back to auto.
That error message is a just generic way of saying it can't get an internet connection. Your TV does not need to know anything about PPPoE (internet connection/authentication method), that's the modem/routers job . The fact that you lost connection while watching TV, and I assume you had no problem with other devices, I think gives us a couple of clues.
It could indicate dodgy DHCP on the optus router because you were actively using the TV at the time (i.e. TV was not turned off), the optus router should have just re-issued the exact same IP address to you TV because it was an active connection.
It could also point to a dodgy ethernet cable between the optus router and the TV, especially given that your TV is the only one with the problem. If it was a DHCP problem I would expect all your devices to be having internet problems at some point. They could be having the problem, but those devices might be better at dealing with it then the TV so its hard to tell. Given that you can't easily access the back of the TV to swap out the cable, you can just switch to wifi instead of wired for the TV using the password on the magnetic card that came with the optus router.
Ok, so perhaps an incorrect assumption from the start. Is anything else in your home connected to the NBN / Modem? I'm thinking its just the TV?
It is sounding like the line is having some problems and the NBN will need to investigate. It could be the modem itslef but with the maintenance having just happened that is looking more like the cause.
You will have to contact Optus directly and request they get a technician to come out and check the line. Let them know the issue is intermittent but persistent and about the recent maintenance that appears to have started the issue.