Problem with 41C

[rprosperi]

Try holding the calculator down pressing firmly/gently on the two outer rails, between the top two rows of keys, and then press the buttons for your testing while maintaining the pressure. If it works while pressing like this, it means one (or both) of the upper posts, or the back of the case (under the feet, where the screws pass thru the sockets) is broken. There are repair options for these problems but step 1 is finding out the cause for sure.

Also, try using other batteries. Even though you think the ones you have are new, one or more cells might be bad or low, leading to shutdown from overall low voltage. Brand new N cells should be about 1.6V or even a bit higher.