My older Vuforia App doesn't work on Android PIE and above

Summary of Problem:

BACKGROUND/ OUR SITUATION:

We created our Vuforia App sometime thru-out 2015 using Unity + Vuforia combo.

Everything works perfect on all versions of iOS (iPhone + iPad)

Everything works perfect on Android devices BEFORE Android 9 (PIE)

PROBLEM:

-->When we open our same Android app with ANDROID 9 (PIE) & above = APP CRASH !!! 

OUR SET UP/ SETTINGS:

Our App was "locked-in" at:

Unity 5.1.4f1

Vuforia 2014-2015 (not sure what version #) it was the (2012-2014 Qualicom/Vuforia scripts)

(please see our attached images for our Settings Info)

OUR APP CONSISTS OF/ IS:

How our app works...

a) our app opens up in a 'ready to scan' scene (camera on, scan line scrolling, looking for Image Targets..., etc...)

b) on start, our app grabs a file (example: "DATABASEassetbundle.unity3d") from our URL (example: "https://website.com/DATABASEassetbundle.unity3d")

c) this asset bundle is a 'books list' of Image Target title (Vuforia's Image Target Manager) in one list

    and the URL (https://website.com/DATABASEassetbundle.unity3d) where we put the .unity3d assetbundle

so basically... as soon as our app/camera comes on, it grabs the latest database list assetbundle, fills in the database, and then our app good-to-go/ in scan mode (ready to detect any of our images on our Vuforia Image Target Cloud list that's online).

...and once image is detected, it pulls in our augmented reality scene (consisting of 3D Models, Sprites, URL links, Videos, etc...)

ADDITIONAL INFO...

1. We've noted that when opening our App on our PIXEL 3 Android 9 (PIE), our App's splash screen comes on correctly, the camera turns on correctly, but then our App CRASHES once our App downloads our DATABASEassetbundle.unity3d file from our URL where the file is.

2. Also... our App's Android Build Settings/ Player Settings's 'minimal API level' only ranges from [API level 9 "Gingerbread"] to [API level 21 "Lolipop"]

-Could our App not working on Android 9 (PIE) be an API issue? 

GOAL:

#1. Get our App working on my PIXEL 3XL! (Android PIE and above)

#1.b. Fix our Unity 5.1.4f1 app  ... and/or...   Get it so our App works on Unity 2019 / Vuforia latest version