Hello. I have a friend whose glider had a seizure a little while ago and then recently had another one. She took him to the vet but they weren't very helpful. Do you know what could cause the seizures? A diet issue or something else?

Seizures in gliders are caused my some knows and some unknowns. Some are from low blood sugar and will go away if the glider is on a good diet.
Some come from stress. A friend has one whenever she is taken out of her cage, so she doesn't handle her much.
Light, loud noises are other causes.