That's because PON uses a different directx dll then other AGEOD titles, afaik.
If you find a Wine (or Proton) setting, that remedies that, do post it. I didn't, and god knows I tried.
I was looking at the AUS army reform event and came across the following lines:
ChgFormedCmdMax = 18;4
ChangeUnitPool = $uni_AUS_Corps_HQ_1805;18
Its part of the Corps formation event. What do the '18' and '4' stand for? Is it the number of corps/armies that may be set up?