If the universe contains no net energy, in what sense can it be said that the universe exists

To our local perspective, it looks like the universe has net energy and exists. But from a global perspective, the universe has no net energy.

To an observer outside the universe, maybe in some higher dimensional space in the multiverse, the universe cannot be observed or interacted with in any way, as such an interaction would require that the universe had some net energy.

If there is no net energy, there is no net mass, and hence no net forces of any kind. To an outside observer, the universe cannot produce any effects on any measurements made, and hence may as well not exist in any scientific sense. This seems to imply that the existence of the universe is relative, and not absolute, does it not?

When you disturb a bowl of water, you create waves but the amount of water is the same yet there are peaks above the average level. When the universe was created, energy and negative energy was created, what we are seeing as the universe are the ripples in the pond.

The fact that to an outside observer, the universe is still nothing doesn't mean that it doesn't exist.

the universe is a seething hive of energy. It is energy which sustains its existence. The universe is composed of matter, energy, sopace, and time. These are all interactive, co-functional and co-dependent. This means that all four factors must exist in order for the universe to exist. If one factor is eliminated, such as energy, the entire edifice will collapse into nothingness... FOOP !!