Hello Matthias,
Which demo GUI would you like to run ?
There are 3 available with your hardware:

You can try to flash the K64F demo FW manually, simply drag & drop the appropriate binary in the FRDM-K64FD drive.
The binary files are located in the Freedom Sensor Toolbox (CE)\Projects installation folders:
C:\Program Files (x86)\NXP\Freedom Sensor Toolbox (CE)\Projects\FXAS21002 Gyroscope Demo\Firmwares\ISSDK\FRDM-K64F_FRDM-STBC-AGM01_21002_2.0.bin
C:\Program Files (x86)\NXP\Freedom Sensor Toolbox (CE)\Projects\FXOS8700 6-axis (Accel, Mag) Demo\Firmwares\ISSDK\FRDM-K64F_FRDM-STBC-AGM01_8700_2.0.bin
C:\Program Files (x86)\NXP\Freedom Sensor Toolbox (CE)\Projects\9 Axis Orientation Sensor Demo\Firmwares\ISSDK\FRDM-K64F_FRDM-STBC-AGM01_Orient_2.0.bin
Then launch the FSTB(CE) and run the associated GUI.
Let me know if this solved your issue.
Regards, Jacques.