I finished Astryl's Tranquility, and the "Zone Progression" thing tels me to return to Ethernia. So I do. But nothing happens. I go to the castle, " The King is not available at this time. Come back and see later" a Chancelor tells me. I returned to Astryl's Tranquility and the Zone Progression said the same thing than before. How can I progress?

That is currently as far as the story progression goes. Time has mostly been going into revamping the pets, festivals and the MegaZone which will hopefully be released in a couple of months. The story will progress again after the site has been recoded. Finishing the current site content however is detrimental to getting into the MegaZone, so congratulations. :D

For now though if you're looking for more to do, I would suggest preparing for the MegaZone. Maybe by gathering max stat pets as well as the best equipment you can find from Dungeon of the Forsaken. The MegaZone will be a temporary zone and will only be available until the complete site revamp has been finished and apparently it's going to be difficult. There was an announcement made recently about it if you haven't checked it out yet.

Thank's! That helps a lot!