Plextools Pro 2.09 Spindown Time

I have Plextools Professional 2.09 and a PX-708A.

The spindown time of the drive according to Plextools is infinite.

Whenever I try to select another choice for spindown time in Plextools, the selection is not remembered. (i.e. when I exit and re-enter Plextools, it’s back at infinity again.)

How do I make Plextools remember the spindown time for the drive?