Configuration

Navigate to Interfaces -> Assignments -> PPPs

Click ➕Add

Link Type: PPPoE
Link Interface(s): (Select the NIC where the cable from your ISP’s modem/router is connected)
Username: YOURUSERNAME
Password: YOURPASSWORD
Check Configure NULL service name

ppp

Click 💾Save

Navigate to Interfaces -> Assignments

For the WAN Interface select under Network port the PPPOE0(NIC) - YOURUSERNAME

assignments

Click 💾Save

Navigate to Interfaces -> WAN

IPv4 Configuration Type: PPPoE
Username: YOURUSERNAME
Password: YOURPASSWORD
Check Block private networks and loopback addresses
Check Block bogon networks

wan

Click 💾Save

You might have to navigate to System -> Routing -> Gateways

And make sure there is only one gateway for the WAN interface. Mine is named WAN_PPPOE.

gateways

I had a faced a problem at some point, where there was more than one gateways. It had something to do with how I had configured my WAN before. Deleted the extra one, gone back to the interfaces we addded/edited, hit 💾Save one more time and everything worked.

Also, I had to set Default gateway IPv4 to WAN_PPPOE Save and reset it back to Automatic and Save again.

gateway-default