I just finished a Dungeon run, and I try to find another Amdapor Keep party with Duty Finder, but I got this error message too.
"Unable to connect to Duty Finder server. Please try again later."

And after that,
"Your registration is withdrawn."

And now...
"You are unable to accept a new duty. Please try again later."

I dare not to relog, because that makes it even worst...