Major Error on Calculator involving Series

[LCieParagon]

I'm not sure if anyone is aware of this error regarding infinite series.

For instance:
The sum from 1 to infinity of
(-1)^(n+1) / n^2 should be pi^2/12
However, my calculator returns an answer of -pi^2/12. Even if I approximate this value, I receive -0.82246...

I am using the mobile version of the HP Prime for reference. I have the actual calculator as well, but I'm at work currently, and my calculator is at my apartment.

Also, (-1)^n / n^2 also returns -pi^2/12, which is in fact correct.

Is this something I just have to live with? I teach Calculus II and Differential Equations currently and I am involved in a unit where I am covering infinite series.

Thanks for any help regarding this matter.