Nook uses Android and there IS NO MORE Flash Player for Android. Viewing Flash content is processor consumptive and it drains batteries, as well as shortening battery life in mobile devices. That's why Android dropped support for the technology.
Android (Google) recommends using either "Dolphin" or "Puffin" browser (they're both free in the GooglePlay store) if you're viewing content that requires Flash Player. They use "server side" rendering to reduce the load on your Android device.