Hi Martin,
K70 has two different USB ports:
High-speed USB port can be accessed using TWR-SER2 board because you need the external USB HS PHY
Full-Speed USB port can be accessed using TWR-SER board
Are u opening the correct project for the USB module that you want?
also inside the documentation folder there is a file called USBHWCONFIG.pdf that shows the correct jumpers configuration for each board and use case.
Let me know if you still have problems and I will post more information.
regards