Some CR2 RAW Files Not Opening; Says Not The Right Kind Of Document

My husband took a bunch of photos on his Canon 80D. Most of them are good, but a number of them won't open at all -- on anything. It probably isn't a problem with IrfanView, but I am hoping someone can at least point me in the right direction. As far as I can tell, I have done everything suggested to fix this problem, but I cannot get any of them to open. I have scanned the media card and it shows no problem. When I try to open the files in IrfanView, I get "Decode error! Not a valid RAW file." When I try to open them in Photoshop, I get "Could not complete your request because it is not the right kind of document." The files are saved exactly the same as the ones that do open. Have you any idea what could have caused this problem? Most of the shots were taken of one of my cats just a couple of days before she died, and I am heartbroken. Thank you for any assistance you can provide.