Android 3.1.1 - Failed resolution of: Lcom/google/android/gms/common/internal/zzbq;

Try adding this dependency to your gradle file:

implementation 'com.android.support:multidex:1.0.3'

Also you should use the same versions for the support and play services libraries. And you should avoid using "+" for latest version. Change this part:

implementation 'com.google.android.gms:play-services-maps:+'
implementation 'com.google.android.gms:play-services-auth:12.0.1'
implementation 'com.google.android.gms:play-services-location:12.0.1'
implementation 'com.google.android.gms:play-services:+'
implementation 'com.google.android.gms:play-services-ads:+'

into this:

implementation 'com.google.android.gms:play-services-maps:12.0.1'
implementation 'com.google.android.gms:play-services-auth:12.0.1'
implementation 'com.google.android.gms:play-services-location:12.0.1'
implementation 'com.google.android.gms:play-services:12.0.1'
implementation 'com.google.android.gms:play-services-ads:12.0.1'

EDIT: You may also add this part to your app level gradle file and try again. I did not see anyone tried this but it may work.

allprojects {
    repositories {
       //...
    }

    subprojects {
        project.configurations.all {
            resolutionStrategy.eachDependency { details ->
                if (details.requested.group == 'com.google.android.gms'
                && !details.requested.name.contains('multidex') ) {
                    details.useVersion "12.0.1"
                }
            }
        }
    }
}

2ND UPDATE: Just seen this, the dependency below, covers all the others, then it may cause a duplication issue. Remove the other dependencies and leave this one:

implementation 'com.google.android.gms:play-services:12.0.1'

I had the same issue and I solved it.Update all your com.google.android.gms:play-services dependencies to 15.0.0. It should look like this:

implementation 'com.google.android.gms:play-services-maps:15.0.0'
implementation 'com.google.android.gms:play-services-auth:15.0.0'
implementation 'com.google.android.gms:play-services-location:15.0.0'
implementation 'com.google.android.gms:play-services:15.0.0'
implementation 'com.google.android.gms:play-services-ads:15.0.0'

Once you do that, it should fix the issue with finding the NoClassDefFoundError error (at least it did for me).

That worked for me I added subprojects block as below to my project gradle file

allprojects {
repositories {
   //...
}
subprojects {
    project.configurations.all {
        resolutionStrategy.eachDependency { details ->
            if (details.requested.group == 'com.google.android.gms'
                    && !details.requested.name.contains('multidex') ) {
                details.useVersion "+"
            }

            if (details.requested.group == 'com.google.firebase'
                    && !details.requested.name.contains('multidex') ) {
                details.useVersion "+"
            }
        }
    }
}
}