Have you tried swapping cages? Dont change anything in either cage as you want all the glider scent to remain the same.
Introductions seem to either go very smoothly and they love each other immediately - or it can take some time and a lot of patience.
Be certain to introduce them face to face in a neutral area like the bathtub. You want to find a place that has NO glider scent on it so no one can claim territory.
Dont stress them. If they dont get along, dont try any face to face for a couple of days. Keep their cages side by side but far enough away they cant reach each other. Keep swapping pouches, toys and cages. Dont give up right away. It took 3 months to integrate Benji in with the girls. Tilly and Weasel loved him right away, so Benji got play and sleep time with them. Tosca was not so sure she wanted to be friends. She finally accepted the fact he wasnt going away and allowed him in. But she acted depressed and scared. I watched her for a few weeks and there was no fighting so I knew everyone was safe. One day, I checked on them and Benji and Tosca were snuggled in one pouch sleeping and Tilly and Weasel were in the other. Finally - Success!!!
Remember there is no guarantee two gliders will ever like each other and get along. This doesnt happen often, but when we get new gliders we have to be prepared to always have two cages.