The message I get is "this app cant run on your computer" black text on a blue background. this happens either with caliber or just on the computer

I have succesfully used deluge for some years. suddenly I am unable to read books I have downloaded. I use caliber to transfer and order my books and read them on a kiddle. I have win 10 on my desk top. The problem has occurred about one week ago. I can read books already on the kindle. I know some ...