The understanding, why formal theories, like string theory cannot lead to some particular solution is quite easy in AWT, if we use water surface model for illustration of Lorentz invariance. Beneath water surface the surface wave cannot spread by causal way. With respect to such wave spreading, underwater appears like void and empty space, while such environment definitely exists from more general perspective of some faster reference interaction. For example the motion of surface waves can be followed and observed easily by using of underwater sound waves, i.e. by using of sonar, because sound waves are spreading approximately 1000 x faster through underwater, then the surface waves.
As we can see, the fact, we cannot observe the (motion / reference frame) of environment by its own waves doesn't mean, this environment cannot exist from more distant (nonlocal) perspective. The explanation of wave character of light and many its properties would require us to believe in hypothetical environment for light wave spreading, although such environment cannot be detected by using of light directly.
The existence of such environment is related to existence of so called hidden dimensions of space-time. For real life example, surface waves are spreading along two-dimensional density gradient, which is forming water surface. While underwater is three dimensional environment. AWT explains the existence of surface gradient by compactification of it.
String theory considers as well, hidden dimensions of space-time are somehow compacted. While this assumption is consistent with Aether concept, I newer find an explanation of that claim in string theory literature, the illustration of it the less. It's evident, string theorists somehow guessed it or borrowed this explanation from particle environment concept unconsciously, while ignoring the rest of connections. The punishment was undeniable.
The existence of Aether corresponds the existence of hidden dimensions for surface waves, because underwater space exhibits an additional dimension, with respect to surface. Therefore every theory (like string theory), which is postulating existence of such additional dimensions is postulating the existence of some hidden environment as well - despite the fact, some proponents of these theories doesn't realize it apparently. Hidden dimensions for energy spreading through vacuum are equivalent the underwater dimensions for waves at water surface.
From AWT follows, Lorentz invariance is a result of strictly local perspective, every nonlocal perspective would violate Lorentz invariance, because such violation is just, what the existence of hidden dimensions means. In real life example, surface waves are dragged by underwater whenever we can consider the existence of such underwater, which becomes a reference frame.
Such conclusion makes string theory deeply inconsistent conceptually. It tries to prove the existence of hidden dimensions on background of Lorentz invariance, which is violating them. This is a simple consequence of fact, string theory proponents didn't understood the subject of their own research, trying to replace the understanding by formal regression of reality based on formal postulates and ideas, collected blindly from another theories.
No wonder, resulting theory has no meaningful solution, because it's based on assumptions, which are mutually contradicting each other from their very beginning for most of nonlocal perspectives (if not all). Instead of this, it leads to huge landcape of nearly infinite number of solutions, thus serving like ineffective and quite costly random number generator. String theorists can only hope, for some limited volume and nontrivial space-time topology the effects of Lorentz invariance will compensate the effects of hidden dimensions - but this is not exact just the approach, which we could expect from proclamativelly strictly rigorous physical theory.
Despite of this, many string theorists are apparently quite proud to their formal approach, tirelessly filling publications by various complex equations. I can tell you, today it's nearly impossible to publish string theory article in peer reviewed press without some formal equations. But for laymans should be warning the fact, we never met with some graphics representation or simulations of their results from obvious reasons - simply because such simulations can never exist! Their equations were be never solved explicitelly, neither plotted in their rigorous formal state. Believe it or not - even after forty years of intensive development nobody has seen even single one example of string modeled by string theory - only some pathetic hand-drawn illustrations copied from first textbooks. And we are talking just about numerical models by now, not about some testable predictions, relevant for physics. But string theorists somehow managed their situation for whole long forty years like alchemists of medieval era, promising Philosopher's stone (Lapis philosophorum) for the rest of society.
Isn't it amazing? I can assure you, this is a true real story of contemporary physics.
Unfortunately, as deeper analysis reveals, other formal theories like LQG theory suffers the same conceptual problems, just in less apparent way - as we can illustrate later. The frontier status of string theory only makes it's internal inconsistency more apparent, that's all. This is partially because string theory is based on special relativity, which is easier to comprehend - then more advanced postulates of general relativity, used in other quantum gravity theories.
The optimist sees the doughnut. Pessimist sees the hole in doughnut. Popper's methodology is apparently based on pessimist approach - it requires us rather doubt then to believe and to see the holes in every theory first. Beauty is always somewhat impractical an violated in symmetry - this is what makes it attractive. From single postulate we cannot construct a vector of logical implication. The theory based on fully consistent postulate set would become tautology undeniably. We could derive each postulate from another, thus effectivelly decrease their count to single one, after then. Therefore no formal math based theory can be completely selfconsistent and as such correct more, then observable reality.
Someone is saying, string theory is beauty and elegant theory. By my opinion, its product of complexity and predictability is suboptimal, as we have a more powerful formal theories already, like the ingenious Heim theory, which handles the concept of hidden dimensions as well, if not better. This doesn't change the fact, every theory brings a new perspectives into our understanding of reality and string theory is no exception. Anyway, from AWT follows, every theory, which expects Lorentz invariance and hidden dimensions at the same moment remains deeply inconsistent, simply because hidden dimensions manifest itself just by Lorentz invariance violation.