OK, after a bit of tweeking, it appears that this is the GeoIP blocking that was responsible for that.
I noticed after a while that in fact, if I was accessing the webpage by forcing IPv4, it was working while accessing with IPv6 was not. So it seems that the filtering on IPv6 is a little bit to efficient.
What happenned was that creating the domain regenered the conf, and in some bizarre way created the issue: if I remove the hook and regen the conf, everything is working fine again.