Could not resolve all artifacts for configuration ':pushwoosh-react-native-plugin:classpath'

I am trying to install Pushwoosh into my React Native app, and I am getting the following error:

> Could not resolve com.android.tools.build:gradle:2.3.3.
         > Could not get resource 'https://maven.google.com/com/android/tools/build/gradle/2.3.3/gradle-2.3.3.pom'.
            > Could not GET 'https://maven.google.com/com/android/tools/build/gradle/2.3.3/gradle-2.3.3.pom'.
               > maven.google.com: nodename nor servname provided, or not known
   > Could not resolve com.google.gms:google-services:4.2.0.
     Required by:
         project :pushwoosh-react-native-plugin
      > Could not resolve com.google.gms:google-services:4.2.0.
         > Could not get resource 'https://jcenter.bintray.com/com/google/gms/google-services/4.2.0/google-services-4.2.0.pom'.
            > Could not GET 'https://jcenter.bintray.com/com/google/gms/google-services/4.2.0/google-services-4.2.0.pom'.
               > jcenter.bintray.com

I am fairly new to React Native and Android development - so I'm not really sure what is going on here.

My main build.gradle file looks like this:

buildscript {
    ext {
        buildToolsVersion = "28.0.3"
        minSdkVersion = 16
        compileSdkVersion = 28
        targetSdkVersion = 28
        supportLibVersion = "28.0.0"
    }
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath("com.android.tools.build:gradle:3.4.1")

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        mavenLocal()
        maven {
            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
            url("$rootDir/../node_modules/react-native/android")
        }
        maven {
            // Android JSC is installed from npm
            url("$rootDir/../node_modules/jsc-android/dist")
        }

        google()
        jcenter()

    }
}

and I followed the instructions on the github.

Can someone explain to me what exactly is the problem here?