Hey 'Sis
What are the OS versions on the Fire 8 & 10, respectively? It’s modified Android, yeah?
I have no experience with Fire stuff but I’ll tell my story with an old tablet, Android 6.01, and tinyCam free & Pro. v2 cams, latest firmware (4.9.9.1851). Maybe something clicks. 
tinyCam 15.1.3 Free
Runs livestream well 3 or 4-up. Plays Wyze Event videos.
tinyCam 15.3 Pro
Runs livestream well 3 or 4-up. Does not play Wyze Event videos: App stalls while loading. Must force stop to exit.
IIRC, versions later than these wouldn’t install from the apks into Android 6.01.
Maybe because (from last May)
Old apks for tinyCam Free are available on repository sites like apkpure - but not Pro.
Here are copies of both I saved (link good for 7 days or 10 downloads) fwiw…