I just bought ArmorPaint today, but have been having some issues.
I ultimately went down to trying to paint a simple box. In this YouTube video, you can see the steps taken - showing the UV map, export, and subsequent failure inside ArmorPaint.
When I turned on the UV Map in ArmorPaint, it looks like was not imported properly:
Yes, armorpaint uses its own .obj parser so it is easier to optimize for me - but sometimes unhandled cases like these still pop up. So it’s great that this issue was discovered and I could fix it!