Pretty sure HBOGO won't work. Netflix doesn't work. Depends on the format, but I'm guessing Amazon Instant Video won't work either. If it's free, give it a try!
Try slideme (is it .org or .com??) or freewarelovers.com for apps, or google the app you want plus apk.
There are a lot of apps that just don't work on the eDGe, for one reason or another. However, there are also a lot that do work!
If your Amazon Appstore app itself isn't working try deleting your edgejr profile with Amazon and redownloading the store app. Or simply delete the app and add it again.
Good luck!