//Add the library in app gradle
implementation 'com.android.support:multidex:1.0.3'

//Add this to the default config in the app gradle
multiDexEnabled true
  
//If this still doesn't work, consider adding this name into the android manifesto
android:name=".MyApplication"

defaultConfig {
    ...

    multiDexEnabled true
}


//In dependencies
dependencies {
	implementation 'androidx.multidex:multidex:2.0.1'

android {
    defaultConfig {
        ...
        minSdkVersion 21 <----- *here
        targetSdkVersion 26
        multiDexEnabled true <------ *here
    }
    ...
}