There is no cantata for Trinity 6 from 1724.  A little research gives the reason: Bach took a trip with his wife Anna Magdalena to the court of Köthen, where they had both worked until their move to Leipzig in 1723.

According to The New Bach Reader, the court account books state the following for July 18, 1724:

“To the Director Musices Bach and his wife, who performed, in settlement rthl* 60”

We don’t know what they performed and for exactly how many days they stayed, but Bach was back in time to compose and rehearse the cantata for Trinity 7 that year.

*rthl = Reichsthaler

Wieneke Gorter, July 15, 2017.