Could multiple plugins cause some problems?

So, I'm trying to implement three different plugins for my game and I'm wondering if they could prevent each others from working. It just seems like when I'm adding new plugins the old ones stop working because of it.

I'm using AdMob, Google Play Games and Facebook SDK.

First I added the AdMob plugin without any problem but sometime after that the ad banner stopped working. And same thing with the Facebook plugin. I've tried it out before but now I can't even manage to login. And when it comes to Google Play Games, the login is the only thing that works.

I have no idea what's the problem but if I've understood correctly it might have something to do with the Android Manifest file. Not sure really. I've tried to search some information about this for a long time but nothing seems to help.

Edit:

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.unity3d.player" android:installLocation="preferExternal" android:theme="@android:style/Theme.NoTitleBar" android:versionCode="1" android:versionName="1.0">
   <!-- Standard manifest stuff here -->
   
   <uses-sdk android:targetSdkVersion="18" android:minSdkVersion="9"/>
 
   <!-- Used to request banner and interstitial ads. -->
 
   <uses-permission android:name="android.permission.INTERNET"/>
 
   <!-- Used to avoid sending an ad request if there is no connectivity. -->
 
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
   
   <supports-screens android:smallScreens="true" android:normalScreens="true" android:largeScreens="true" android:xlargeScreens="true" android:anyDensity="true" />
   
   <application android:icon="@drawable/app_icon" android:label="@string/app_name" android:debuggable="true">
     <activity android:name="com.unity3d.player.UnityPlayerNativeActivity" android:launchMode="singleTask" android:label="@string/app_name" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen">
       <intent-filter>
         <action android:name="android.intent.action.MAIN" />
         <category android:name="android.intent.category.LAUNCHER" />
       </intent-filter>
       <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="false" />
     </activity>
     
     <!-- MAKE SURE YOU INCLUDE THE FOLLOWING SECTIONS FOR FACEBOOK -->
     <activity android:name="com.facebook.unity.FBUnityLoginActivity" android:configChanges="fontScale|keyboard|keyboardHidden|locale|mnc|mcc|navigation|orientation|screenLayout|screenSize|smallestScreenSize|uiMode|touchscreen" android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen">
     </activity>
     <!-- You can change your Facebook login screen orientation here -->
     <activity android:name="com.facebook.LoginActivity" android:screenOrientation="portrait" android:configChanges="keyboardHidden|orientation" android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen">
     </activity>
     <activity android:name="com.facebook.unity.FBUnityDeepLinkingActivity" android:exported="true">
     </activity>
     
     <!-- Make sure you change the AppID to yours -->
     <meta-data android:name="com.facebook.sdk.ApplicationId" android:value="\ 1435117936777980" />
     
     <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>
 
     <!-- AdMob -->
     
     <activity android:name="com.google.android.gms.samples.ads.GoogleAdsSampleActivity" android:label="@string/app_name">
     
     </activity>
     
     <activity android:name=".BannerXmlActivity" android:label="@string/banner_in_xml"/>
     
     <activity android:name=".BannerCodeActivity" android:label="@string/banner_in_code"/>
     
     <activity android:name=".InterstitialActivity" android:label="@string/interstitial"/>
     
     <!-- Activity required to show ad overlays. -->
     
     <activity android:name="com.google.android.gms.ads.AdActivity" android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"/>
     
   </application>
   
 </manifest>