Imoen and Neera are both level 20. I've accumulated a few different spells for the 9th Circle - Power Word Kill, Time Stop, Wish, Spell Trap, Wail of the Banshee, and a couple others. Neither of my mages can copy any of the spells into their spell books. Neera has Dragon Fire or whatever, due to an ability I picked. But other than that both their 9th Circle pages are blank. I'm not running any mods or anything.
I've attached a ToB save, Neera has a few 9th Circle scrolls in her inventory that neither her nor Imoen can read.