After taking several assessments and being told that all signs indicate he is perfect in every way for a career as a high school teacher, Mike becomes a high school teacher.
He is miserable. Why is Mike so miserable in a career that psychological assessments
indicated he would be a perfect fit?

Although Mike would have some characteristics that would help him be good in teaching, it's not guaranteed that it will be enjoyable for him. Psychological assessments should be treated as suggestions and not a method to make an important life decision on.

the game was released on september 15, 2015 for microsoft windows and os x, and on july 17, 2016 for linux. fox expressed interest in releasing undertale on other platforms, but was initially unable to port it to nintendo platforms without reprogramming the game due to the engine's lack of support for these platforms.