Problem: Not routing GND pins despite GND power plane
I'm hoping someone can point me in the right direction to help solve this strange routing failure.
I am trying to route a small board (~5 x 3cm) with SMD components on both sides. The board population is not very dense and, from experience, it should be not overly difficult to route as a Class IV, 4-layer board (1 Gnd powerplane & 3 signal planes).
As expected, there are a few signal nets that could not be autorouted. However, it seems it cannot route most of the "GND" pins/nets to the power plane, even when there is no restriction on the use of vias. The software generates a lot of vias, too much, many of them uneeded. It is not a simple "lost" net issue as it manages to connect a few GND pins/nets to the power plane, but not always the same ones.
It is very frustrating as it looks like a "no-brainer" to connect the GND pins, and indeed feels like a simple configuration problem, but I have tried many options, including going to 6 layers which seems to make routing even worse.
I'm still on V3.0.