Network doesn't work without internet

My ISP provided an ONU Huawei Smartax MA5698 which connects to pfsense that runs as my firewall and router. I realised that when there is no internet from the ONU the lan computers can’t communicate. For example when there is no internet no one can print from the printers on the network. But when i turn off the ONU completely the lan works even without the internet. Can anyone help me try to resolve it? is it a configuration in pfsense or the ONU from the ISP. thanks

Do you have the ONU handing out IP addresses in the same IP space as your pfsense?

I can’t tell. It was configured by the ISP. How can I check

Connect a machine to the lan port ONU and see what IP address your machine gets.

Configure the wan port on pfsense to be dhcp or fixed ip address, and make sure you untick - Block Private Networks & Block bogon networks

PFsense can not have the same IP address range configured as it will conflict

The WAN is connected via PPPoE. does it still apply?

What device is authenticating the ISP link - ONU unit or do you have to do this PFSense.

Ask your provider, how to setup your internet with a third party router.

I was told I needed a 3rd party router. So I used the pfsense as the router. There is a username and password for authentication to get access to the internet

On your screenshot you have configured the connection as IPV6, should this be IPV4 ?

Have you connected pfsense to the correct port on the ONU