2. "No connection" means the neigbouring Macroelements can even overlap without any resistance.

I'm modelling a four-point bending test with interfaces using ATENA Engineering 2D. When I given interface properties to the line as 'No connection' the model is not running properly, that is I'm getting zero displacement but a very little increase in the reaction force, when I plot the force vs. displacement curve.
Contrary to this, when I give interface properties to the same line as 'tensile strength = 0, cohesion = 0, friction = 0.5', then I obtain a proper force vs. displacement curve but still values aren't satisfactory.
My main concern is with these two methods I mentioned above. What exactly is the difference between these two techniques, as I want to check the behavior of a composite concrete slab in case of a perfect bond and also when there is no bond between the two concrete layers?

Also, when I'm assigning different values to the interface properties, the results I get don't vary with each other.
I expected some change in the load carrying capacity of the composite slab undergoing 2 point loads (four-point bending test), when I vary the interface properties!