To unblock the FireStick streaming device you need to make a so-called jailbreak. It sounds strange, but there is really an effective way to help you use third-party streaming apps on your Amazon device. I found an article with a detailed description of this process, you may be interested in learning about this
https://www.firesticktricks.com/jailbreak-fire-stick.html in more detail. I've tried everything in this article and it seems like it worked.