I wonder where you bought your tickets. Can you tell? Because as far as I know the official seller was Eventime and they sent the tickets by mail. Or did you ordered the tickets just very late, so that they can’t sent them via mail anymore?
I found this information on the webseite Festhalle
Kartenvorverkauf an der Festhalle
(ticket presale at the Festhalle):
60327 Frankfurt am Main
im Eingang City der Messe Frankfurt (neben Messeturm)
(at the entrance “City” directed next to the “Messeturm”)
It says presale, so I don’t know if that is the right place for you. Where did you ordered your tix?