Have you tried Nook Study?
Can't see my books on my PC. Never had this problem until recently. Need the larger format for some of my selections. Tried everything.Even had IT try to make it work. The messages from others don't give dates. Please help
Do you mean you can't get them to open with Nook for Web, Nook for PC/Mac or NookStudy? Or, do you mean you can't get them to download to the app? Nook for PC/Mac has been kind of flukey for awhile in downloading, but it will eventually do it. Sometimes you have to just keep trying at different times. Also, not all eBooks are available for all the apps.
BN stopped supporting Nook for PC/Mac earlier this summer. They are just letting it rot away according to an article I read a few weeks ago. When I find it, I will post the link.