[POE2] Last boss atlas book not dropping

I have been killing bosses using t16 waystones on corrupted/irradiated maps (over 20 times now) and the last atlas point book is not dropping. I have 4 points into boss difficulty and still no joy.

i believe this may have happened due to 2 earlier books dropping at once when i fought a duo of bosses, though when i picked one up the other disappeared.

please help! ive also tried reapplying my atlas passive points.

Same, stuck at 4 poitns and ive been doing loads of T15s, 16s, 17s 18s

Same for me