I have owned 12c's since the 80's. I purchased a new 12c in July 2018 and since then the numbers didn't always register when pressed. I didn't return it right away because I didn't want to drive 35 miles to return and thought the buttons would break in or I could remedy. I changed batteries and reset, but the problems persist. I can't afford to have an inaccurate calculater. I called Office Depot and they said the warranty expired. Has HP 12c quality deteriorated since the 1980's? Does anyone else have this problem?
The warranty for a new HP 12C is one year. Since you bought it new from Office Depot in July 2018, it is still under warranty until July 2019. If an Office Depot employee disputes this, ask for a manager, and show them the one-year warranty in the back of your 12C manual.
Disclaimer: I don't work for HP. I'm just another happy HP calculator user.