Heyyoooo! So my White Face, Magnum, had her twins come OOP about 5 days ago (since noticed they detatched from the nipple). They were both covered in fur (not their stomachs yet) and no one has their eyes opened. 2 days OOP I noticed one of the twins on the bottom of the cage, cold and crying. The other was in her pouch. I put him back in the nest and a few hours later, I saw him on the bottom of the cage again and Magnum just didn't seem to care when I brought him to her. I also noticed that he seemed a little dehydrated so I decided to start hand raising him. Unfortunately he passed away the next day. He had a small internal birth defect, no one could've done anything.
Anyways, last night the other twin opened one of his tiny eyes, the other is closed. Magnum would come and cuddle him and bathe him after running around for 10-15-20 minutes at a time. Now today he's on the bottom of the cage. I noticed one of his little fingers is slightly swollen with a scratch mark on the bottom of it. I took him to her and she would lick him, he'd go on her back or try to go for milk then she'd jump around and he'd fall off. She'd check on him and then go off somewhere else. Glock (father, standard, not a first time father) bathed him and then went into the nest with Magnum. It's been almost an hour and no one has come to check on him. He's also not crying though? Should I start handfeeding this little one? My gliders aren't inbred,, Magnum is a first time mother, I have her on a 50/50 diet. (Half protein, half fruits/veggies)

She might not have enough milk, in which case you should supplemet feed if they keep on taking care of the joey.
1 hour seems quite a long time for both parents to ignore the joey, but I've seen mine do it for up to 2 hours. However, if you hear him cry and that it does not get a reaction from the parents, then you will need to hand raise him.
Check if he is not cold or dehydrated, which could be a reason why he is not crying.