Unable to install a modified apk file
The generated APK file by apktool needs to be signed before you can install it on a Android phone or emulator:
First you have to create a key-pair for signing stored in a keystore (only required once):
keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000

Note this command uses keytool for JDK. source
Then you have to sign the app using apksigner which is part of the Android SDK:
java -jar build-tools\29.0.3\lib\apksigner.jar sign -ks my-release-key.keystore &lt;apkfile&gt;

Now you can install it on the device:
adb install &lt;apkfile&gt;

If you have the original apk file installed on device you have to uninstall it. because of the changed signature you can install your modified apk file over the already installed original file.