Hello Tom,
if you use only S32 Design Studio, it is nearly impossible to secure the device. S32DS does not modify UTEST flash area.
At first, check you have correctly installed and update PEMicro drivers.
Which debug probe you use?
If you use Multilink Universal or Multilink Universal FX, please disconnect jumper J5 in debug probe.
Which version of S32DS you use? version 1.0 or 1.1?
What is your microcontroller mask?
Did you try to use another microcontroller?
Regards,
Martin