In the point deduction section of the AP Music Theory exam guidelines, it says:
The 6th or 4th of a 6 4 chord is unresolved or resolved incorrectly.
What exactly does this entail?
It's a little unclear exactly what you mean, but I'm guessing this is in reference to the cadential or pedal (also known as "neighbor") six-four chord.
Typically, these chords resolve to a root-position triad, and the bass doesn't move, but the upper voices do.
And typically, these upper voices will move down by a step each: the 6th above the bass will resolve down to the 5th above the bass, and the 4th above the bass will resolve down to a 3rd above the bass. This correct resolution is shown at A below.
Incorrect resolutions would have both of these pitches either moving up or moving down by skip. One of these is shown at B above.