Internet only works if I disable and enable WAN, after, it doesn't

[andre_x]

I've setup a new OPNsense instance.
The WAN is connected to a fiber ONT (PPPoE). It receives the IP and the default route is there.
Internet is not working. If I launch a ping to 8.8.8.8, it fails. Traceroute doesn't reach any hop.
If I leave the ping pending, disable the WAN and enable it back again, when I go into diagnostics I see that the ping works and keep working, but if I stop and start them again or if I launch a new one (always to 8.8.8.8), they don't work.
Whaaaat?
What could have I done wrong?