hmm...I'm not at home right now to look, but you may be stuck doing command line (no fret).
you'll need to attach the vlan to your WAN interface with a command like:
set interfaces ethernet eth0 vif 201 pppoe 0
Take a look at this POST as it may help you narrow it down. I'm not sure which interface you're using for WAN vs. LAN so you'll need to match either eth0 or eth1 accordingly.
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