Hello @emb02
What version of Flash Magic Tool are you using? Please, make sure you are using the latest version available from the Flash Magic website.
How are you generating the .hex file? Please, try the following: import hello_world demo application from the SDK into MCUXpresso IDE and build the project. Expand Debug folder, right click on hello_world.axf file > Binary utilities > Create hex. Try using the generated .hex file with Flash Magic Tool.

Also, what is the procedure you are following to enter the device in ISP mode? I used the following configuration in Flash Magic

I connected a USB cable to J8, then press and hold ISP0 (SW4) button while pressing and releasing the reset (SW1) button to enter UART/I2C/SPI ISP mode; then, I browsed for the .hex file and clicked on Start.
Regards,
Eduardo.