What sort of problem would drive a near omnipotent civilization to seek an "outside the box" solution?

The Setup

A while back, I read an article in which the author compared the rise and fall of civilizations in the universe to a forest.

In the forest, small plants come into being, grow, and die over relatively short time spans. Living in the shadows of much larger trees, these small plants compete with one another for the basic resources of life: sunlight, water, and carbon. The large trees, on the other hand, tower over the forest floor and have, compared to the smaller plants, an unlimited supply of resources. The forest, then, is a hierarchical ecosystem dominated by the ancient, firmly established trees, in which the smaller plants (and smaller trees) are just sort of along for the ride. When one walks into Redwood National Forest, after all, he most likely notices all the giant trees before noticing the shrubbery. (I wouldn't know for sure, as I've never been. It's on my List).

Similarly, the Universe is teeming with many small civilizations that continually rise and fall over the course of millennia... but only a relatively few civilizations that have reached the top of the Foodchain (capital 'F').

My story concerns such a civilization... let's call them the Foo for lack of a better name, as I'm a computer programmer by trade, and some habits die hard.

Let's say that, by our reckoning, the Foo are at level somewhere between III and IV on the Kardashev scale, and have the agency to affect change on a universal scale. These people built and abandoned Dyson spheres long ago. They have engaged in stellar architecture, creating both the art and the engines of their economy with the very stars themselves. Now, they are well into the age of galactic engineering. They have intimate knowledge of the nature of reality itself, hard won over countless mega-years of evolution.

Now, though, the Foo have a Problem.

The Problem

Spoiler alert: I do not know what the Problem is. Perhaps it is the impending heat death of the Universe. Perhaps it is something utterly alien to my own limited understanding. I just don't know. This is the specific question for which I am currently seeking guidance.

The Out of the Box Solution

All of this, I must confess, is to serve as the backdrop for the story I really want to tell. The Foo, you see, facing an existential threat whose solution lies beyond their own understanding, must seek an "out of the box solution." Well, perhaps it would be more precise to say that the Foo have decided to seek an "inside of the box solution."

Being so keenly self-aware has given the Foo an insight that just might save them: they realize that they have reached the limits of knowledge they are capable of obtaining from within the context of their own experience. They understand that, although they are nearly omnipotent, they are still bound by the "baggage" they carry from the previous stages of their evolution. Without outside help, there will always be questions for which they lack the proper context to answer (or even know to ask).

As it happens, the Foo have decided to devote their entire economy to constructing a full scale simulated reality of a new universe, simulated at the quantum level in full fidelity. Their goal is to monitor the evolution of all of the civilizations that arise therein, observing them through all the various stages of evolution until they discover one with the potential of solving their own particular Problem.

Although this concept is ripe for further questions and discussion (what is the substrate of this simulation? What is the level of precision? How can they possibly assimilate all that data? What if the Foo are already in a simulation? How does time pass in the simulated reality compared to the Foo's reality?), I really just want to focus on the nature of the Problem for now. The other stuff will come as this idea germinates.

Thank you for your time. I very much look forward to joining your community.