Quite baffling. If the material/texture can't be loaded you should be seeing a red and black checkerboard in Babylon.js.
Also the flame sprite clearly works which is also being loaded from a spritesheet within the Files folder, just like the billboard.
Anyone else having similar issues?
Did you always install the plugin and behaviors by dropping the c2addon file into the Construct window or are you doing it manually?
I tried mismatching the Plane behavior (older version) with the current plugin but all that did was messing up the animations of the billboard.
At this point I cannot reproduce the completely transparent billboards you are experiencing. Unless you changed things in the capx itself, which would be obvious...
Sorry I can't help you any further right now.
