Just in case someone else might have the same problem this could be due to an intestinal blockage.
Intestinal Blockage: Don't hesitate make sure you do as instructed and get to a vet ASAP.
Abdominal fullness, bloating, or swelling
Diarrhea (if blockage is not complete)
Absence of passage of stool (when blockage is complete)
The partial or complete mechanical blockage of the small or large intestine. The bowel is physically blocked. This most often occurs in sugar gliders when a foreign body is present in the intestines (such as wood, seeds, or millet), blocking the bowel.
A foreign body, such as seed husks, seeds, millet, or wood, physically blocks the intestines, allowing fecal matter to build up in the intestines
Never give gliders inexpensive dry cat food
Moisten dry foods for easier digestion
Steer clear of seeds, nuts and other dry foods (however I know many of us do feed pecans but I read that Peanuts also carry a contaminate so peanuts are just not worth the risk this of course would include peanut butter.
I would appreciate knowing what your vet said please so I can also learn.
I'm not able to list all the research data but here is most of it.
"Sugar Gliders: Gotta' Love 'Em", Kevin Schargen, former President, ISGA, Critters Magazine
Again we should all seek veterinary care immediately! which your doing but don't wait or think it will get better because they can die. Gliders don't show pain easily as it is a danger to show weakness to predictors or their community. So when you see a sudden bloating or aggression, pain, lethargy its probably pretty bad.
Good luck and best wishes please keep me posted thanks,