thanks I solved the issue by adding in the manifest what is said in radiusnetwork site.
<service android:enabled="true"
android:exported="true"
android:isolatedProcess="false"
android:label="iBeacon"
android:name="com.radiusnetworks.ibeacon.service.IBeaconService">
</service>
<service android:enabled="true"
android:name="com.radiusnetworks.ibeacon.IBeaconIntentProcessor">
<meta-data android:name="background" android:value="true" />
<intent-filter
android:priority="1" >
<action android:name="eu.reply.engage.example.blebeacons.DID_RANGING" />
<action android:name="eu.reply.engage.example.blebeacons.DID_MONITORING" />
</intent-filter>
</service>