It seems Fire Stick has blocked my ability to allow “apps from unknown sources” with their last update. The “allow button” has been removed.
You have to activate developer mode activate ADB debugging, then click Install unknown apps and click on the app you want to use to install your apk and allow.
settings>My Fire TV>About>Fire TV Stick 4K Max ( click on your device name 7 times to activate developer options)>click “return” on the remote>scroll down to the just activated “Developer options”
Have fun and STREAM ON!!!
Please review this for all firestick issues and guides, if the following hasn’t worked feel free to ask.
This should resolve most to all issues.