question

You can get release md5 by doing some tweaks to your app build.gradle file.

The only way proper md5 is generated is by going android studio --> gradle tab on top right corner --> executing signing report as answered by @Levon@Amazon. On executing signing report you will see md5 generated for Variant : debug but in case for Variant : release it just show Config : none.

The solution is that you need to tell the gradle file about your signing credentials (keystone, passwords). Here are the steps

1) Copy your release keystore file in project --> app directory

2) Then in your app build.gradle file add your signing credentials

android {
    compileSdkVersion 28
    buildToolsVersion "28.0.3"
    defaultConfig {
        multiDexEnabled true
        applicationId packageName
        minSdkVersion 19
        targetSdkVersion 28
        versionCode appVersionCode
        versionName appVersionName
        compileOptions {
            sourceCompatibility JavaVersion.VERSION_1_8
            targetCompatibility JavaVersion.VERSION_1_8
        }
    }

    signingConfigs {
        release {
            keyAlias 'YOUR_KEYSTORE_ALIAS'
            keyPassword 'YOUR_KEYSTORE_ALIAS_PASSWORD'
            storeFile file('keystore') //Assuming your keystore file name (copied to app folder) is "keystore"
            storePassword 'YOUR_KEYSTORE_PASSWORD'
        }
    }

3) And then in your app build.gradle

buildTypes {
    release {
        minifyEnabled false
        shrinkResources false
        zipAlignEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        buildConfigField "boolean", "IS_DEBUG_ABLE", 'false'
        signingConfig signingConfigs.release    // Add this line 
    }
    debug {
        // this means proguard is active or not
        minifyEnabled false
        shrinkResources false
        zipAlignEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        buildConfigField "boolean", "IS_DEBUG_ABLE", 'true'
    }
}

4) Now click the "Gradle" tab in the top-right corner, expand your app's entry, then expand Tasks, then Android, and double click on "signing report". It will now generate MD5/SHA1/SHA-256 for both debug and release variants.

I had some trouble with this, eventually figured it out in Android Studio but I actually figured out how to solve this right from the command line without Android Studio. This problem will be more common as keytool doesn't give the MD5 anymore and over time more and more people won't have the old version that gives the md5 value. Anyway, openssl can convert it for you if you pipe the keytool output to it, and at first looks different than what amazon wants in the md5 field but I verified and it's the same value.

Run Command:

keytool -exportcert -v -alias alias -keystore "path\to\keystore\my.keystore" | openssl dgst -md5

The output will be a 32 character string, with no colons ":" in it, and Amazon is looking for 16 2 character hex values separated by ":". So just add the colons every 2 characters and there you will have your MD5 value. You should also upper case the letters but I don't think that matters (not sure). Those with Android Studio signing reports can verify.