If there was no mass/energy would space time still exist? In other words, does on space time only exist because of an interaction between two points of energy?
A spacetime without mass or energy is the one described by special relativity.
Whether such a thing could exist or not (as a real thing rather than a useful approximation) is unverifiable, since we aren't in such a spacetime and have no access to any other, even if they exist. That means it's outside the realm of science, at least at our current level of understanding.
I think a better question is "could there be spacetime w/o energy". The answer is yes according to the field equations. Now, the same is true for EM in that electromagnetic fields can exist without charges but it's less clear they would exist if there were no charges. I guess my point is that the field equations need to be supplemented with reasonable and consistent boundary conditions.