Android app crashes on start after adding Unity Ads 3.1.0

Build runs successfully but then app crashes on start

from logcat:

Code (CSharp):

1.     java.lang.RuntimeException: Unable to get provider android.support.v4.content.FileProvider: java.lang.ClassNotFoundException: Didn't find class "android.support.v4.content.FileProvider" on path: DexPathList[[zip file "/data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/base.apk"],nativeLibraryDirectories=[/data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/lib/arm, /data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/base.apk!/lib/armeabi-v7a, /system/lib]]
2.        at android.app.ActivityThread.installProvider(ActivityThread.java:6678)
3.        at android.app.ActivityThread.installContentProviders(ActivityThread.java:6220)
4.        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:6135)
5.        at android.app.ActivityThread.access$1200(ActivityThread.java:235)
6.        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1768)
7.        at android.os.Handler.dispatchMessage(Handler.java:106)
8.        at android.os.Looper.loop(Looper.java:214)
9.        at android.app.ActivityThread.main(ActivityThread.java:6981)
10.        at java.lang.reflect.Method.invoke(Native Method)
11.        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
12.        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)
13.     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v4.content.FileProvider" on path: DexPathList[[zip file "/data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/base.apk"],nativeLibraryDirectories=[/data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/lib/arm, /data/app/com.Saiked.Headbouncer-pGLQL1fxJKT5U8WKhjQ6hw==/base.apk!/lib/armeabi-v7a, /system/lib]]
14.         at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
15.         at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
16.         at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
17.         at android.app.AppComponentFactory.instantiateProvider(AppComponentFactory.java:121)
18.         at android.app.ActivityThread.installProvider(ActivityThread.java:6662)
19.         at android.app.ActivityThread.installContentProviders(ActivityThread.java:6220)
20.         at android.app.ActivityThread.handleBindApplication(ActivityThread.java:6135)
21.         at android.app.ActivityThread.access$1200(ActivityThread.java:235)
22.         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1768)
23.         at android.os.Handler.dispatchMessage(Handler.java:106)
24.         at android.os.Looper.loop(Looper.java:214)
25.         at android.app.ActivityThread.main(ActivityThread.java:6981)
26.         at java.lang.reflect.Method.invoke(Native Method)
27.         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
28.         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)

EDIT: Reimporting all seems to fix this problem