Today I started working again on a old project of mine. It's a ball game using newton physics. Years ago I builded my game in A6, now I wanted to use A7. It worked good until I re- compiled the level. Now every physics object falls through the level. How can I fix this?

Maybe, your version of newton works only with blocks, and now you compiled the level as mesh?

I've checked and tryed it. I compiled as block and as mesh and in both cases the physics objects just fall through.