Nook Simple Touch Glowlight

[mizfiesta]

I've been on the internet for hours tonight with my Nook trying (unsucessfully) to download books from kobo rakuten using ADE.
I have had to give up as I'm getting nowhere. I got the book onto the Nook itself multiple times but it wouldn't open and displayed error message "Sorry, cannot open this book". I read advice about renaming the file etc to no avail. So now I just want to chuck the Nook in the bucket. The only reason I'm not is because my Daughter bought it for me years ago so it has sentimental value.
I keep thinking I may be able to figure things out since B&N then Sainsbury's left us in the lurch but I give up.
Has any face multiple issues like myself? Has most people binned their Nooks?