At school, I am making an app for a competition with Sentinus Digital and Digital Futures and a few days ago it was the semi-finals (WE ARE INTO THE FINALS!) but we couldn't get our app to work on the school's tab 4 devices. The app I'm creating uses: PersonalImageClassifier1, Camera1, TinyDB1, TextToSpeech1, WebVeiwer1, TextRecognition1, and Player1. The image classifier is from the "Picaboo" tutorial and the text recognition is from ML Kit Text Recognition Extension. We have downloaded the APK file via USB but when we try to open it it just says that it won't, no proper error message just that it won't. Can someone please explain why and how to fix it?
What android version is this Tab 4 running?
It won't download by usb or won't install?
Have you tried installing over WiFi using the qr code and the companion app?
I think the Android is 4.4.2 KitKat (it's in school so I can't check.)
It will download and install but won't open.
When we try to download via the QR code it doesn't work because it won't recognise the QR code for some reason, probably because the camera app is too old but we could try installing a QR code scanner.
When we use the companion app it gets stuck loading at 20%.
Try downloading the apk to your pc then sending it to yourself in an email and logging in to that email on the device, if it's a school device it is probably better to use incognito mode, or you can log in to mitappinventor on that tablet, compile the project there and download the apk. Btw i do not know if the app you made will work, that is a very old Android version! But you should try anyways.
Or just transfer the app to the tablet via USB.
Wait, I am posting this 3 months later, didn't notice 
Me neither