Why is my app screen black when I build to Android? What am I doing wrong?

Hello, everyone. I have been working on an AR app since January of this year. I began the build using Unity 2017.3 and Vuforia 7.1.35. After a while, I kept running into some issues that I couldn’t work out so I took a break from it. I came back to the project in late summer and I was able to work out those particular bugs. I tested the app on my phones, and it worked as designed, minus a few cosmetic issues. I fixed those cosmetic issues, but before I had a chance to export the app to my phones again, I absent-mindedly upgraded Unity to version 2018.2.1F1 and that’s where the problems began. When I test it in Unity, the app works just as I intended. The models track, the sounds and animation play and pause on cue, the links work, and most importantly, the camera works. When I build and run to my Android device(s), however, everything is black. In earlier builds, all of my scenes would load fine leading to the actual AR camera scene. The three most recent builds have all resulted in a black screen immediately after the app opens. No splash screens or anything. I’ve tweaked my build settings and player settings numerous times to try to weed out the problem, but no luck yet. I’ve also scoured the Unity and Vuforia forums for help with the issue, but even still, I have been unable to find a viable solution. Everything I read was either outdated, pertaining to iOS, or not even answered at all. So, I am posting this question to hopefully get some solid answers for myself and anyone else who may be having this issue. Please help!!!
I am testing my app on a Samsung Galaxy On5, a Samsung Galaxy S7, and a Samsung Galaxy S8 Active. I should probably also note that my S7 and S8 phones have updated to the newest Android version since January and some time in the summer. I don’t exactly remember when. I am happy to provide any other specific details if necessary. Thank you.

Hello, everyone! I am glad to announce that I was able to work out the issue with the Android black screen. I’m still not exactly sure of what the cause or cure was, but the problem went away after I followed these steps. The first thing I did was update my Vuforia software to 7.5. After restarting Unity, I opened a test project that I had been working on with the previous Vuforia. I then reimported all of the updated core samples and AR/VR samples. I successfully tested the user-defined target and the image target scenes in Unity, and on my phone(s). I made notes of Vuforia’s default settings and I compared them to my notes from my project’s camera, player, and build settings. From there, I adjusted my settings to match the Vuforia settings. I THINK, and I could be wrong, that the issue was in the Player Settings, under the Other Settings tab. For Target Architectures, I had all 3 selected (ARMv7, ARM64, and x86), and that’s when the app would load, but the camera would be black. Whenever I unchecked ARM64, everything worked beautifully. As I said, I don’t know if that was the direct cause, but that’s how I worked it out. If you’re having the same issue, hopefully, this works for you, too.