Dehydration! Raise the humidity & don't try to force off any eye-caps. It can take a long time for sunken eye-caps to regain their proper convex form, & once damaged
this way, some never do. Stick with it.

IF there are any stuck eye-caps layered on (& I cannot be sure there is) it's safer to let an experienced herp vet take a look at it- it's a very delicate procedure to remove
them IF needed, & many owners have accidentally done far worse permanent damage to their snake's eyes when trying to fix this on their own. But first, raise humidity
& be patient.