actually 怎么也 like 怎么, is an interrogative tone, and complaining tone,,
like 我怎么也没有想到为什么。means " i have no idea with that and iits spend me lot of time".a kind of like that meaning..
怎么也不 like complaining tone or tone of emphasis..
e.g. i wouldl hang out with friend at 11 am,but when i wake up is already 12 pm, so i may complain my friend "why dont u call me to wake me up"
"why dont u call me to wake me up." this sentence in there like chinese 你怎么也不叫醒我, is kind like the complaining tone...
i hope that will help u ^^