Problem with bluetooth keyboard

I have the old Apple bluetooth keyboard (It's the same thing as the new ones, except it takes 3 batteries instead of 2, I was unaware there was even an old one when I bought this) but anyways I bought this about 3 months ago refurbished, and about a week ago the command button, "z" , "x" , and "c" buttons just stopped working. I was wondering if there is a way to fix it. I opened up the keyboard viewer and the buttons do not change colors like when I press any of the other keys. And to save you guys the trouble of asking. I tried my keyboard on two different macs, has the same problem, I replaced the batteries twice, and I tried another apple bluetooth keyboard on my macbook and it works just fine, and it is not damaged because I haven't spilled any liquids on it and I haven't dropped it either, it's been sitting on my desk a majority of the time since the day I got it. If it helps, when those buttons first stopped working if I hit the "c" button hard enough, it would still work, but not anymore.

I tried looking online, but I cannot find much on this, and I cannot return it or anything like that because the return policy / warranty was only 30 days.