Ever since the overhaul of the questlines it wont let me accept Adventure awaits in Serendia despite the Balenos quests above it being completed (88/88) when i do try accept it then it'll send me to the Black Spirit who doesnt have the quest either, has anyone else experienced this or know of a fix pls?

did you ever find a fix? im afraid im having the same issue on one of my characters.

I'm also having this issue hopefully they fix it soon.

Hi there, could you scroll down and check, if you have the old serendia questline (including calpheon) open somewhere on that character? If yes, you first have to complete that questline before the new serendia mainquest unlocks.

do you have not completed missions on the [II] quests? 

I also have this issue, and going to the NPCS mentioned doesn't help either. I also have the special growth quest in my uncompleted quests tab, but I cannot accept that either.

Can you show all the quests youre still missing in the main quest tab? Also, is your character a former season char?

I cannot remember if the selected character was a season character or not, as I have had her on my account for years. Here is my quests folder showing my completed main quests as well. As you can see, I have just completed the Belenos Breaker of Chains questline, and I cannot accept the special growth or the Serendia quests.

The old calpheon questline also stops the serendia quest from being acceptable, and it goes on beyond what is shown on the screenshot. So it would be nice if you could add another screenshot until you are starting with Mediah, simply to see if there is anything left open.

I had the same issue. I contacted Pearl Abyss support, and they told me I needed to complete the old Serendia and Calpheon questlines. They told me the next quest I had to do,(sometimes the next mission from the old questline aren't listed in the quest log). and from there I was able to finish the old questline and solve the problem. You can try to ask  to Pearl Abyss support too.