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 ^^

怎么也  how could u be  that？？？？

怎么也不 it means not

我想想哈。。。你有一点点断章啊

首先，“怎么也”---怎么也想不通---IT means 实在是想不通， 怎么怎么都想不通

                        今晚，怎么也睡不着

表示，已经努力了，但是没有效果，实在没办法了。

“怎么也不”---都下课了，你怎么也不提醒下我呀。    

                  怎么也不会原谅你。

                  他都吃那么多，怎么也不胖。

这个比较难解释，呵呵，说多了就好了。