Is it possible that dark matter is made up of "failed" solar systems?

No. "Dark matter" is not composed of protons, neutrons, and electrons.  "Dark matter" may not even exist; scientists keep devising experiments to determine its character, but many elementary particles have been excluded.

The motivation for the "dark matter" hypothesis is that distant galaxies appear to rotate "too" fast -- at least, their far arms seem to orbit the galactic centers at speeds that don't match the likely mass of luminous material in the galaxy.  Therefore it is supposed that there must be some invisible mass holding the galaxy together.  Why don't the far-out, fast stars just escape into interstellar space?  The dark matter hypothesis has been around for nearly 100 years, but a small number of cosmologists are always looking for other solutions.  A somewhat viable competitor is the MOND hypothesis of Mordehai Milgrom, and related ideas of Erik Verlinde.

Look up "MACHOs".

This was proposed a long time ago. Since then, a survey -- looking specificaly for evidence of dark matter being made of dark world made of ordinary matter -- was conducted.  Some were found (for example, rogue planets), but well below the quantity needed to explain the effects of dark matter.

The more likely candidates are "WIMPs"

No,

but it and the fabled "black holes" are made up of shortcomings in our understanding of gravity.

It's what the MATTER of Parallel Universes IS, RELATIVE to our own universe and each other.-------It is detectable because, according to M theory, GRAVITY is the only force or "quality" SHARED by the matter particles of parallel universes , which, otherwise, do NOT interact with each other at all.

Indeed, it is this gravity, apparently from nowhere, that suggested the existence of "dark matter" to begin with.

The WI in WIMPs stands for "Weakly Interacting"   as they interact only weakly via gravity and nothing else.

Think of Parallel universes as universes sharing the same "space", just as different radio station signals share the same "Air".  The only "real" one is the one we are "tuned to"(share attributes with).   All the rest are still just as real in the absolute sense, but not to us.

Dark matter came into the astronomy jargon when Vera Rubin in 1970s discovered the outer stars of a spiral galaxy are speeding at the same rate as those near the center. And at the same time, no stars are being launched away because of centrifugal forces. The only probable cause of this phenomenon is, as scientists put it, the existence of matter that we do not see within a galaxy; and this matter holds the stars together and maintain a constant speed both at the edges and near the bulge at the center.

Many things were and are being hypothesized. Even failed stars (brown dwarfs) that can not be observed because of their very dim light, or WIMPS which stands for Weakly Interacting Massive Particles. Of course anything we can not see could be attributed to dark matter, failed "solar systems" as you said. So why can't we theorize also a non-baryonic matter that does not reflect light and is all around and compensates for the "missing" matter that holds a galaxy together?

If it was failed solar systems, it would be visible.  Normal matter (which is what solar systems, failed or otherwise, are made of) can be detected through the light or other radiation it reflects.

Dark matter does not reflect any light or radiation.

If it were made up of simple debris, it would have some sort of heat signature to go along with it, and have a corresponding amount of hydrogen - it's how we mapped the Milky Way using radio emissions from hydrogen gas... and, that's not seen - at least, not in the amounts that correspond to the apparently huge gravitational pull that's evident. 

It is my understanding that most scientists do not seem to think that dark matter is normal matter. They think dark matter is WIMPs.. Given that there are many brown dwarf stars that never reached the main sequence and rogue planets with no stars I suspect that dark matter may be a combination of normal matter and exotic matter. Sometimes the simplest explanation turns out NOT to be the correct explanation. Entropy and chaos means Occam's razor fails the null hypothesis test.