I have included the stack-up.
Layer 7 is a plane with net +1.8V.
Layer 11 is a plane with net +5V.
Layer 12 is a plane with net -5V.
Layers 1, 2, 3, 5, 9, 14, 16, 17, 18 are signal layers with polygon net GND.
Layers 4, 6, 8, 10, 13, 15 are true planes with net GND.
When enabling view of a single plane layer and I can see an X over the via, does that mean it is connected or not (attached screen capture).
I have a rule for power planes and polygons with the first object: IsVia and (InNet('+5V') or InNet('-5V') or InNet('+1.8V'))